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00:03
Welcome. Hi, I'm Mikki and this is Mikkipedia, where I sit down and chat to doctors, professors, athletes, practitioners and experts in their fields related to health, nutrition, fitness and wellbeing and I'm delighted that you're here.

00:24
Hi everyone, it's Mikki here, you're listening to Mikkipedia and this week on the podcast I speak to Dr Grant Tinsley about the accuracy of body composition measurements. We discuss the body composition scales you have in your bathroom, how they stack up to what is considered gold standard measurement techniques, and how much weight we should put on the numbers that are provided by your at home bathroom scales.

00:53
compared to say the in-body assessment that you get done at your gym. And we also discuss protocols for ensuring better reliability of the numbers that you are getting and how these will reflect your overall body composition progress. We then discuss another area that Grant is heavily involved in, which is intermittent fasting for active populations, including both men and women.

01:22
So this was really a great all around discussion for anyone wanting to understand their body composition data better and also for those interested in intermittent fasting. So for those unfamiliar with Grant, he is an associate professor at Texas Tech University, the director of the Energy Balance and Body Composition Laboratory and is a certified strength and conditioning specialist and certified sports nutritionist. He has over 150

01:51
peer-reviewed journal articles and abstracts, with his major research interests being sports nutrition strategies, body composition assessment techniques, and intermittent fasting in active populations. Hence our conversation today. So I will pop links in the show notes to where you can find Grant over at his website, GrantTinsley.com, and there is also a link there straight to PubMed and Google Scholar for his research.

02:20
and also Grant's Instagram account where he is I would say moderately active on. But anything he posts is super interesting. So that's how you will find Grant. And just a reminder, the best way to support this podcast is to hit the subscribe button on your favorite podcast listening platform. That increases the visibility of the podcast out there and amounts to literally thousands of other podcasts. So more people get the opportunity to learn from the guests that I have.

02:50
on this show. Alright team, please enjoy this conversation that I have with Dr Grant Tinsley.

03:04
Thank you so much for taking the time with me this morning. In fact, I am in Christchurch about to go and watch some bodybuilding show tomorrow, of which our mutual friend, Eric Helms, is beginning his first of about 48 shows he's doing in about eight weeks. Yes, that's very exciting. I didn't realize you would get to be there in person and I'm sure that will be a great way for him to kick off his competitive season. Totally. And of course,

03:32
I saw you both together on, I believe, your feed, and I was like, ah, mutual friends. So I knew that this would be a great conversation to have about your interest in intermittent fasting, which is very unrelated to that topic, but body composition techniques, and all things sort of health and fitness, which is really cool. So Grant, can we start with just getting a little bit of your background? How did you get interested in diet, intermittent fasting, and or...

04:01
you know, things are related to body composition. Was it sort of through your own interest in sport or was it sort of the other way around? You started learning about it and then you started working in that space. Yeah, I think it was honestly some of both. So I was involved in sports growing up, always enjoyed watching sports. My dad was very into sports. My mom was to some extent, she wasn't as big of a fan, but was a swimmer herself from back in the day and water polo player.

04:31
So I had this interest in that in terms of more say fitness specifically, you know, when I was 11 or 12, I began to develop an interest in nutrition and lifting weights just because of kind of an increased awareness of, you know, how it could change my athletic performance or my physique or so on. So I had an interest in that, that kind of continued to develop throughout my adolescence. And I also, I've always been a nerd. I love school. I love every subject in school.

04:59
but science was a favorite of mine. So when I went off to university, I was studying physiology just because I loved the human body and wanted to learn more about it. And then I added a degree in nutritional sciences as well. So I was learning a lot about the human body, about nutrition. And then I was also learning from a lot of other people, say in the gym. I had never been in a situation where I had lifted weights for sports or had much guidance in terms of sports nutrition. And

05:28
kind of structured exercise. Even though I exercised, I didn't truly know what I was doing in terms of programming. So it was kind of this interesting combination of learning more about the practice and seeing what other people have been exposed to, as well as learning about the body and nutrition. So that kind of continued on through my educational journey. So I studied, as mentioned, physiology and nutrition in my undergraduate work. And then I went on to study biomedical sciences in my master's program.

05:55
And that certainly gave me a greater appreciation for the human body because it involved a lot of cadaver dissection. So I spent a lot of time just a lot of time with anatomy and physiology. And then in my doctoral program is where I truly had my first, I guess, formal training and exercise because I studied kinesiology and exercise nutrition. So throughout all this formal education and some additional certifications and sports nutrition and strength and conditioning.

06:23
there were kind of these parallel paths being walked with the formal academic side and in my own kind of personal interest in applying some of this information. So in terms of intermittent fasting specifically, my first doctoral advisor at Baylor University, whose name is Paul LaBounty, he's a good friend, he had been the first author on a position statement on meal frequency that was written for the International Society of Sports Nutrition. So I had seen this and this

06:53
I was also interested in this kind of unique doctoral program that really combined nutrition and exercise because I hadn't seen too many of those. So I went to study with him and kind of came in at a time where there was sort of a shift from this idea that a very high meal frequency was needed in all settings, whether it was athletic performance, weight maintenance, health. There was sort of this prevailing view that you needed to eat frequent small meals throughout the day.

07:19
In the position statement, some of the conclusions were related to evidence not necessarily supporting that, that it was a little bit equivocal or there weren't clear benefits of these higher meal frequencies. So that's where we came in. So he and I had lots of discussions about the other end of the spectrum. So if we saw that a very high meal frequency may not be necessary in many cases, at what point does meal frequency matter? If you go low enough, do you get to a point where you're compromising?

07:49
adaptations to exercise or seeing adverse effects. So that's sort of the background of when I arrived there and began conducting some work in this area. And that's just continued on over the last decade or so. Yeah, and Grant, like I understand you do, you consult to companies. Do you also do individual sort of consults and things like that? I don't typically for sort of family and friends, I will, but that's not really part of the...

08:16
Most of that consulting is more statistical analysis or help with kind of sports nutrition products and things in that realm. Yeah. Okay. Because I always wonder with people sort of in your position, you're very heavily involved in the research aspect and what the literature says. But of course, and you'll see this regardless of whether you consult with people or not, like there'll be the anecdotal stories of friends and family. And so you'll be reading something and...

08:44
other things will be happening over in this sort of like, I suppose, there's other evidence, but it's not necessarily sort of research-based. Do you see much of that with some of your work or not so much? I do. I think, yeah, I do think, you know, when you're in this area, many people are interested in sharing their own kind of personal anecdotes or questions and have some interesting views sometimes.

09:12
I don't know, middle of the road approach. There are many individuals where they've found some type of nutrition or exercise paradigm that works for them. It's helping them move towards their goals and I'm happy for them. Even if what I'm hearing them say isn't always entirely consistent with how I view the literature. I know there's a little bit of an art to it, the literature informing our recommendations, but then tailoring that in the individual.

09:37
So, yeah, in terms of my work, I stay sort of more on the research and evidence-based side, but in terms of the individual application, I try to be relatively accepting of different viewpoints there. Yeah, I really like that. It's like the art and science of nutrition. So with intermittent fasting, lots of different sort of thoughts around the effectiveness of effectiveness and why it's effective.

10:07
your definition of intermittent fasting? So what are we actually talking about Grant? Yeah, that's a great question. And I will try to give a short answer, but first I'll preface it by saying that it's not a short answer. My own definition has evolved and you'll certainly see this used differently, not only in kind of the general online fitness community, but in the scientific literature. So this has been, and this is.

10:32
This is probably true in other areas where there's sort of inconsistent terminology that has to be refined over time. But I was actually privileged to be part of this large international consensus project that's been going on for a couple of years. And we're about to submit the paper for this study. It involved about 40 international experts on fasting. And we went through five different rounds of surveys as well as some additional kind of online discussions to refine.

11:00
kind of our usage of all these different terms related to fasting. So this included defining all these different variants of fasting, trying to come to a consensus. And we're ultimately going to put forth this paper as a recommendation for consistent terminology so that if someone is looking at a research study about fasting and they're using this term and kind of referencing this framework we provided, we have this consistent definition where we know what we're actually talking about.

11:28
Because if you look at the current literature, the term intermittent fasting is used very frequently and you don't typically know what is meant by that unless the authors have provided sufficient detail in the methods. So with that long background out of the way, I would say that intermittent fasting, even as we define it in this consensus statement that will come out, and I'll mention Daniela Koppel in Berlin, Germany was the leader of this project. So she certainly deserves the lion's share of the credit for wrangling.

11:57
40 of us together and trying to keep us on track through all these discussions. Both that said, kind of the definition we came up with or agreed on with intermittent fasting is that this is a broad term, including programs that use repetitive fasting periods with each individual fasting period lasting up to 48 hours. But the implementation is fairly flexible. This could be a single day a week program. This could be multiple consecutive or non-consecutive days per week.

12:26
This would include paradigms like alternate day fasting, where you fast either completely or complete a modified fast every other day. And it would also, by this definition we're proposing, include paradigms like time-restricted eating, where you just have a restricted eating window each day. And I'm not sure you've seen, but I think most people I talk to who are not in this research space, if they're just familiar with intermittent fasting from, say, popular press,

12:53
they often think of time-restricted eating specifically. And even at specific hours, often they'll say, oh, intermittent fasting, that's where you eat from noon to 8 p.m. every day. It's this very narrow definition that would fall under that umbrella, but is not the entirety of the definition. Yeah, I know that makes that, you're absolutely right, I hear that quite a bit. And the fasting-mimicking approach is interesting, and it's, I mean, I'm well familiar with it, but people get confused because they're like, well,

13:22
can you be eating but you're fasting? So can we talk about the physiological changes that occur during intermittent fasting and how modified fasts also fall into this realm? Yeah, that's a great question. So a few components there. First, just for the listeners, when I say modified fasting, it means a period where there's a substantial energy restriction, but some energy intake is allowed.

13:50
By a very strict definition of fasting, this would not be fasting. Many people take this stance and I don't blame them for it that modified fasting might not be fasting because you're eating something. But typically as it's employed, if there was a modified fasting day, this might equate to someone eating about 25% of their weight maintenance calories. So very low calorie, lower than you would want someone to go if they were employing the same degree of energy restriction every day. This is often applied as a single meal.

14:18
The origin of this came through, I won't go too far into the weeds here, but some of the early alternate day fasting research. One, it's relatively difficult. Alternate day fasting can be you eat on Monday, you don't eat on Tuesday, you eat on Wednesday, you don't eat on Thursday. So entire calendar days where you're not eating from the time you get up to the time you go to bed. That's a substantial challenge. And some of these early studies also showed more lean mass loss than we would like to see in a weight loss scenario.

14:47
So both for the compliance side and also for lean mass preservation, that form of fasting, alternate day fasting morphed into alternate day fasting where instead of a complete day of fasting, you would mostly fast, but you'd have one moderate size meal that would contain about 25% of your weight maintenance calories. So in one sense, you're definitely still achieving a large energy deficit, even if you have these modified fasting days.

15:16
paradigms including modified fasting are more so targeting that energy deficit you're achieving rather than staying for a prolonged time in the sort of physiological state of fasting, which we can talk about. The fasting mimicking diet, which you mentioned is interesting because it's relatively low calorie, not quite as low calorie as 25% of your energy needs, but it's low calorie and there are the ideas that you're consuming.

15:44
certain foods that will sort of minimize your absorptive response, sort of minimize your body thinking that you're no longer fasted. So for example, low carbohydrate and moderate to low protein foods and kind of foods that are supposed to be formulated in such a way that you won't have these large kind of postprandial or post-eating physiological responses that would sort of tell your body that you're no longer fasted.

16:13
Again, the idea is you can maintain a pseudo-fasted state, even if you are consuming food over the course. It's often employed over, say, five days every few months. Yeah, like Volta Longo's Prolon Fast. Yes, exactly. Yeah. Grant, do you think, sorry, just before you go on into some of the benefits, when I think about fasting, there's that circadian biology fast.

16:42
that is seemed to be removed from the fat loss or the weight loss fasting benefits. And that to me implies or suggests that you would want to do a complete fast of anything but water because you're doing it for a different reason other than the calorie deficit that comes with fasting that is one of the main benefits of fasting for people interested in fat loss and stuff like that. Yeah. It's really interesting.

17:09
issue mentioned. So we do have kind of these different areas of interest in intermittent fasting and they do overlap. Because as you're mentioning, on one side, some people treat this understandably and even justifiably based on a lot of the literature, treat this as just a different way to restrict calories. On the other side, there are many people trying to implement this, say researchers trying to implement this in such a way that it's not really about the calories. It's about...

17:36
circadian rhythms and eating at a time when your body is better able to process the nutrients, able to process the nutrients more effectively, have kind of better say blood glucose and lipid responses to a meal. So that's more of the circadian focus. Now there's certainly overlap and a good example of this that's, you know, as we mentioned, a very popular form of intermittent fasting is time-restricted eating. So there will be some settings where time-restricted eating might be employed to...

18:04
say minimize nighttime eating or shift more of the energy intake earlier in the day, sort of for these chronobiology or chrono nutrition reasons. But depending on the person's diet prior to starting this program, it may also cause energy restriction. So there are a number of studies where there might be health benefits that are seen and it's not entirely clear if this is solely because of an energy deficit or if there is this kind of chronobiology benefit.

18:33
And there have been a few studies that have tried to tease us out. And, you know, I know you mentioned briefly last line in email, one of these forms, which is early time restricted eating. There have been some trials where the researchers intentionally try to limit, say changes in weight, and they're really just focusing on shifting the nutrients. And there have been some benefits seen in those cases, not across the board. But that's one area of research that's kind of still being teased out from the scientific perspective, less from just the.

19:02
behavioral perspective, but scientifically, is this just another method of calorie restriction that's more complicated and for some people less enjoyable, for other people more enjoyable? Or are there these unique benefits related to our timing of nutrients? Yeah, because I've seen research that shows us the liver isn't as good at metabolizing carbohydrate later in the night, and so therefore we're going to get a higher blood glucose response.

19:32
But I suppose these early time restricted feeding studies almost paint that picture, but other studies wouldn't suggest that it makes too much of a meaningful difference. I'm not sure what your thoughts are on that. Yeah. I think I would say what I'm about to say is my view on a lot of areas of intermittent fasting. I think it depends a lot, even though in research we're looking at group level things. We're looking at a whole group of people fasting, a whole group of people following a normal diet.

20:00
But really we need to know something about the individuals and what they were doing prior. So if you have an individual who say struggles with nighttime eating and what I mean by that is they're eating a large percentage of their total energy in a day and lots of their nutrients, say after dinner or late dinner and continuing to snack after dinner, say up until midnight. And you put someone like that on a time restricted eating program where they have to stop eating at 8 p.m.

20:26
That could set them up for a host of beneficial changes related to health, body weight and so on because they're limiting their eating opportunity. They're even implications for food selection. There are many individuals who might tend to be kind of on track nutritionally throughout the day and then at home, you know, after work or school or what have you. They have access to more foods. They have time. Maybe they're watching TV and they can tend to not only overeat, but maybe overeat on things that aren't.

20:55
necessarily the most nutritious, nutrient dense items. So in that context, for example, some might see a big improvement from going on a time restricted eating program. There are others where there are individuals who are either already following a program that would be similar, like maybe they don't eat after dinner and being allowed to eat till 8 p.m. would actually be extending how late they're eating during the day or where it just wouldn't change it that much. So for them going on this program relative to what they were doing before,

21:24
maybe it's not actually that much of a change. So then we wouldn't expect to see much difference in various health markers, body composition, and so on. So just as a broad principle in terms of the individual application, I think it certainly matters what someone was doing prior to these programs in terms of what they're eating, food choices, timing of the foods, and so on. Yeah, no, that makes perfect sense. So Grant, outside of the calorie deficit that you mentioned, what are some other physiological benefits?

21:52
that occur with fasting and with that sort of intermittent fasting that we're discussing. Yeah. So in the human literature, I would say I would characterize the human literature as neutral on fasting. There are some studies where there might be isolated benefits of fasting itself. Lots of those are in the realm of early time-restricted eating, which we could talk about. I don't think it has.

22:18
great potential to be a strategy that would be easy to follow for a lot of people. Of course, we know adherence and kind of these behavioral aspects are really critical anytime we're talking about nutrition. So even though it's interesting proof of concept, you know, may not have wide application. Taking those out of it, taking the early time restricted eating studies out of it, most trials have not really demonstrated a clear advantage of fasting protocols as compared to energy matched protocols.

22:48
say normal calorie restriction, where you're not necessarily changing the eating window or the meal frequency, but you're just reducing the energy content at each meal. Now, again, this is a group level thing, and many of these human studies, we haven't seen these clear benefits, but at the individual level, there's certainly people who'd find it either easier or harder to follow a fasting program.

23:11
So with all that said, that's the human side, but there is a lot of literature, say rodent literature and other model organisms that have shown really profound benefits of fasting. And this is where some of the optimism has come from. And this is why there are a large number of human trials trying to replicate some of these benefits. However, it's very difficult as in other areas of research to directly apply what we're seeing in rodent work to humans.

23:37
And part of that from my perspective is related to the duration of fasting. So there'll be studies in rodents where they might put the rodents on a time restricted eating protocol where they're consuming all their calories in say six to eight hours a day. And then we don't, and they see say profound health benefits compared to control animals. We don't always see those profound benefits in humans, but these same fasting durations are being used in rodents and humans. But it's really not the same physiologically.

24:07
So an overnight fast or 16 hour fast in a rodent would be like several days of fasting in a human based on the differences in our metabolism. So my opinion is that many of the human studies are probably stopping the fasting periods a little bit short of where we'll see more interesting physiological changes that could actually cause a unique benefit of fasting. And we've summarized, we wrote a review on this at one of my doctoral students, Matthew Stratton and I, and several of our...

24:35
other team members wrote an article on this, kind of looking at in humans, the studies we have of the physiological responses to an acute, like a single period of fasting. And in many cases, some of these physiological changes, they start kind of after an overnight fast, but they tend to ramp up once you exceed about 18 hours of fasting. So for many of these popular implementations of fasting, such as time restricted eating, with an eight hour eating period and a 16 hour fasting period,

25:04
These fasting periods may be stopping just short of where some of these more profound physiological changes occur. That's something I'm personally interested in for future fasting research is some of these longer, but maybe less frequent fasting periods in humans and seeing outcomes that would be more similar to some of the promising things we've seen with rodents in shorter fasts.

25:32
sort of a 20 hour fast and a four hour eating window type study, like would that elicit some of these benefits? Would that be long enough? That would be one option. I think some people could adhere to that without problem. It would be a challenge. So another option would be something like, you know, once a week having a little bit of a longer fast, like once a week getting up to a 24 to 30 hour fast, but doing that once a week or.

25:58
a couple of times a week. And there are some studies like this. These are forms of fasting that have been studied, but currently there's a lot more research, I feel like, coming out with, what I view as kind of moderate time restricted eating protocols where you have an eight hour eating window. And again, for some individuals, they might naturally have an eating window that's not very different than that. So if you took someone that naturally eats over 10 hours each day and just restrict that by two hours to eight hours each day, that's not a major difference for them.

26:26
in most cases in terms of what they're intaking, when they're intaking it, and so on. Yeah. And Grant, what are your views on fasting for that long and the potential for bone and muscle? Are there any concerns there that you share that I know that others voice around the idea of fasting if you're over 35, for example? Yeah, that's a good question. So there are the early, like 100 years ago, fasting literature.

26:56
It seemed to indicate that major losses of protein weren't an issue for a couple of days. There are newer studies with more sensitive measures showing where, you know, we might have increased protein degradation earlier than that. It's also another kind of line of research that would be, I guess, critical of fasting is related to protein timing and frequency in these muscle protein synthesis responses.

27:23
There are lots of acute studies here showing that, oh, it might be optimal to ingest protein every three to six hours. If you're going these long periods without stimulating muscle protein synthesis, this would be a concern. With that said, the actual trials, and we've conducted several of these looking at exercise training combined with different intermittent fasting programs, haven't shown clear detriments of lean mass when protein intake is sufficiently high.

27:51
So in most cases that has been at or above 1.6 grams per kilogram body mass. And we've seen, for example, trial we did here in resistance-trained females looked at time-restricted eating with a eating window that ended up being about seven and a half hours each day compared to a group that was required to consume breakfast. And their eating window ended up being about 13 hours a day. And over the course of eight weeks, both groups had

28:18
equivalent increases in fat-free mass, muscle thickness, strength improvements, and so on. So in some of these applied studies, at least in the short term, this was an eight-week study, we don't see a limitation on lean mass being gained in this case. And in other studies, lean mass being maintained. So this is often the case, but sometimes there's a disconnect between kind of the short-term mechanistic trials looking at, say, protein synthesis and protein degradation.

28:47
versus these more concrete outcomes over time. So those are just a few thoughts related to that. I think, you know, I'm a huge proponent of exercise, of course. So exercise would go a long way in any weight loss scenario. Exercise and maybe resistance exercise in particular would go a long way towards maintaining skeletal muscle mass specifically during an energy deficit. So I'd certainly recommend that for anyone. And I think that would go. That paired with sufficient protein intake.

29:17
and not too extreme of an energy deficit. All those together would be a good scenario for at least maintaining skeletal muscle. Yeah, no, that's great, Grant. I definitely want to get back to chatting about your study with the resistance-trained females. Do you think that an extended fast, like the one that you're interested in studying, for someone who is carrying quite a lot of excess body fat is actually...

29:43
not as detrimental as someone who might just have like 10 pounds to lose. I don't know, the potential for being detrimental was going to be less and someone who has a lot more of that sort of stored energy. Am I right in thinking that? Yeah. I think that, no, I would agree with that, particularly if we're talking about lean mass and things of that nature. I think there is literature to support that, that leaner individuals may be susceptible to greater lean mass loss during these large energy deficits where, as you mentioned,

30:12
individuals with higher adiposity, it might be less of a concern. Yeah, yeah. Cool. So Grant, getting back to your trial, I found this really interesting because of course, so often it's, you know, you read about in sort of popular media and social media, the detriments of fasting for females. Was that what you were, was that one of your sort of things that you were looking at with that trial specifically is to see if any detrimental outcomes?

30:41
In a way it was, this study was exclusively in females. So in this particular study, we didn't have a head-to-head comparison to see if the changes were better or worse than we saw in males. But as mentioned, I would say it was a positive result in terms of time-restricted eating being a viable strategy, even in the context of trying to increase lean mass. But you're right, it is very common to see, you know, like, oh, intermittent fasting is okay for males, but not for females.

31:10
You know, sometimes, you know, in popular press, it's not clear where the origin of this is, but there were some early trials, I don't know, probably 15 to 20 years ago with a form of fasting called 5-2, which would essentially be two days a week of either complete or modified fasting. There were a couple trials that showed potential sex differences in maybe some less favorable, I believe it was blood glucose responses in females as compared to males.

31:40
So I think that for people who are looking at literature, sometimes they point back to those trials. With that said, an enormous amount of the intermittent fasting literature is actually being conducted in females. A good example of this is Dr. Krista Verdi, who's a leading researcher in fasting, has conducted a lot of trials, first on modified alternate day fasting and then now several on time-restricted eating.

32:04
Where she recruits from, they typically have the vast majority of their participants being female. And in a number of studies, they've shown good health benefits, body composition benefits, and so on of intermittent fasting protocols. So I would say there's not a large, to me, not a large amount of strong support showing very clear sex-specific effects where you would say this is recommended for males and not for females.

32:33
Now, again, you could find some literature to support it, even the acute fasting work I mentioned. There are cases where you see sex-specific responses, but my opinion is that nothing there in the acute trial or even in the long-term trials we've had would be strong enough for me to say like this should be discouraged for females and encouraged for males. With the normal caveats, it's certainly at the individual basis and talking about unique

33:03
pregnancy, breastfeeding, other health considerations, a number of things that would certainly contraindicate fasting. But just looking at sex alone without any of those specific scenarios, I personally don't feel the literature is particularly convincing in terms of this being detrimental for females. Yeah. That's so interesting, isn't it? Because there are definitely voices who would suggest the exact opposite. And I also wonder what population they're talking to as well. Like if you're talking to an already lean female.

33:32
who is trying to fast and train and unable to meet a sort of sufficient calories to support that, then that's never going to go well. But I don't think that'll go well regardless of whether you're male or female. I don't think that's sex specific either. I'm not sure. Yeah, that's a great point. And many of the trials I mentioned when I said there have been many in females, many of those admittedly were weight loss trials. So there were individuals who had overweight or obesity.

34:01
rightly pointing out a moment ago, might be individuals who be set up to have better responses or less of these concerns. Certainly, as you're mentioning in active females and particularly an area I'm interested in, there's been a little bit of research in this, but not a lot would relate to like disorder eating behaviors. And I'm sure in some individuals, there'd be the possibility of exacerbating some eating behaviors that would be detrimental. The group level data I've seen has not supported.

34:31
intermittent fasting being a cause of disordered eating or being associated with adverse outcomes and questionnaires. But again, I'm sure at the individual level for some individuals, it may exacerbate, whether it's binge eating tendencies or extreme restriction methods and so on. Like any program, I think the individualization and application would certainly be important here. Yeah, for sure.

34:59
Grant, did your study, was it looking at weight loss as well and were your participants in a calorie deficit or were they on maintenance calories throughout? Yes. So, they were very near maintenance calories. Looking at body mass in the time of strategic eating groups, it stayed completely stable with a little bit of fat-free mass gain and fat mass loss.

35:25
Our original intention was a very slight calorie deficit, I believe 250 kcal per day. What we saw, which is not a surprise, even when we provided food scales and taught people how to weigh their food and so on, most of the diet records were coming back with greater energy restriction than that. We know there are major challenges with monitoring energy intake and free living settings. So we were seeing weight remaining stable, but people were reporting energy intake that

35:53
resting metabolism and activity which we had measured appeared to be lower than the deficit we wanted. So, it's one of those things where you design the study on paper and you think, okay, this is what we'll do. We'll employ this calorie deficit. But then you hit some wrinkles where it appears they have this greater calorie deficit, even though the remaining weight's stable. So, it ended up being where we weren't particularly tinkering with the energy intake. We were limiting the eating windows. We were providing supplemental protein. But in the end, it came out where, again, body mass was very...

36:22
very steady, did not change, but we did see this increase in fat-free mass and slight decrease in fat mass. Yeah, nice. And Grant, one of my questions was sort of, do you think that we've learned all we need to know about intermittent fasting? But of course, you have mentioned just before that you're wanting to do some of these sort of extended fasts as trials to sort of investigate what happens there.

36:48
Is there anything else that you're excited to investigate in this area? Yeah. So, as a researcher and someone whose job is research, I'll never say that we know everything we need to know on any topic because I don't want to be out of a job. But yes, the prolonged fasting, I say I have an interest in it. I will say these studies are very hard to conduct. So this is why we are very interested in fasting. We do these trials periodically, but our lab has several other lines of research.

37:14
It's very challenging to do these studies in real life. So I have no immediate plans to do these longer term fasting studies. I hope someone will do them. It might end up being me, it might not. But yeah, I think a continued area that needs to be refined is sort of considering how we're setting up studies. There's sort of different paradigms here. One, and we've sort of alluded to both of these. One is the scientific side. And the scientific side to me, there's still remaining questions on

37:43
are there unique benefits of fasting itself on health in humans? Beyond energy restriction, beyond those simple factors, can we control for those and actually see a meaningful health benefit in humans? Now that takes a lot of control, typically ideally be done in a laboratory environment, even inpatient providing all the foods, very expensive, very complicated studies, but they would answer an important scientific question.

38:11
On the other end of the spectrum, we have more generalizable studies, studies we can conduct that would apply more immediately to the general population. And these would be focused on behavioral aspects. For example, if we give individuals who might need to lose some weight, if we give them simple instructions, such as eat all of your calories between noon and 6 p.m. each day, is that a sufficient behavioral strategy to cause say energy restriction, weight loss associated health benefits and so on?

38:41
Or in athletes, is this a strategy that would allow for maintenance of lean mass and performance at a slightly lower body mass? Some of those questions that are more, again, behavioral nature or just implementing a simple program. So to me, there's some research that's targeted both of those sides and I think those both need to continue to advance. I think the purposes of those studies need to be clear. Sometimes people try to kind of split the difference and...

39:08
do both studies at once. And as I've mentioned, it's very difficult to be confident about things like energy intake in free living humans where people are out about living their lives. So I do think there's a lot of potential. My interest primarily is in active individuals. So, you know, we've done several trials with resistance training individuals, several with endurance training individuals have been conducted as well. But I certainly think there's more information we could gain about whether or not this would ever be a beneficial strategy.

39:37
And if so, kind of in which context this might be beneficial. So last area I'll mention there is, as I've sort of said, more in the broad, say weight loss, health improvement realm, we've seen a lot of studies where there was not a clear group level benefit of intermittent fasting protocols. However, I think that existing data sets might be able to be used for this, but some of this will have to be new trials.

40:02
I think an area we can prove is looking at what factors might predispose someone for success on one of these programs. It could be related to their eating patterns prior to the study, could be related to kind of subjective or psychological factors. If we could identify these through questionnaires or say physiological responses to an acute fast, if we could identify some of these features that might indicate someone's more likely to find success on one of these programs.

40:31
that might be useful in terms of the application, say in a weight loss clinic and they're counseling someone through what method of energy restriction might be useful for them. I could go on, but those are just a few thoughts, areas that I think we can continue to research and get some interesting answers. Yeah, no, I completely agree. And particularly looking at that individual response is so important because we are individuals and not like averages, as I know lots of people like to say, and I like to say as well.

41:01
Grant, before we move on, just to, as you know, I've got a whole list of questions on body composition, but I actually will just focus on one, which I get questions on a lot. Can I just ask you about your endurance trials? Any surprising findings from some of your endurance and intermittent fasting trials or things you weren't expecting or major take homes? Because I have quite a lot of endurance athletes who would listen to my podcast and be interested.

41:32
Yeah, so I've only been directly involved in one of these, but I'm aware of several others. In general, most of these trials have utilized eight hour time restricted eating. So consuming all calories in eight hours per day. The one trial I was involved in, the data collection occurred in Italy in the lab of my good friends and collaborators, Antonio Paoli and Tatiana Moro. And the kind of interesting finding from that, and this would be consistent across these other trials as well, is that

42:00
That eight-hour time-restricted eating was sufficient to produce a small energy deficit and corresponding weight loss. In the trial in Cyclus, this was the one conducted in Italy, there was an increase in relative peak power output. So essentially, peak power is maintained at a lower body mass. So peak power relative to body mass improved, but absolute performance did not change with time-restricted eating versus a controlled diet.

42:30
So in that sense, there could be some promise for individuals, if there are individuals who might need to reduce body mass or whose overall performance, say in cycling, would be improved by having a lower body mass and they could maintain power output. So some select applications there. Other trials from other labs and runners have seen similar things where this might be effective for producing a smaller energy deficit. And of course, that's not always a good thing. There are many athletes where we would not want an energy deficit.

42:57
we'd be more concerned about a missed eating opportunity, for example, or missed fueling opportunity. So some caveats there, but that'd be kind of with broad strokes, some of the big picture findings. Yeah, no, that's awesome. And of course, when I pop up this show, I'll put your research gate in the show notes, so interested people could have a look at the research you're talking about. So Grant, obviously you're busy in the lab and in your other, in another area of research is the body composition techniques.

43:26
So the one which I get a lot of questions from clients and people is on the percent body fat. So they jump on their bathroom scales. It gives them a scale weight, but it then calculates the percent body fat. And people get very sort of...

43:48
interested over what happens across the course of a week and they get very involved in trying to understand how their body fat percentage goes up, goes down. Can we talk a little bit about what's being measured and some of the benefits and limitations of that? Because it's such a common measure that people use. Yes. So, conceptually, body composition is important and more important than say weight alone.

44:18
We know that there are two individuals that could weigh exactly the same and have very different health and performance that's related to some extent to body composition. Now we can't always estimate body composition accurately. And the situation you're describing is very common where the techniques individuals have access to are not always the accurate techniques. These at-home body fat scales typically use a technology called bioelectrical impedance analysis.

44:47
So they have these little typically silver electrodes on the scale. You'll step onto the scale. And while the assessment is being conducted, a small imperceptible electrical current is passed into the body and then received back at the electrodes. And based on what the scale knows injected into the body and based on what it's received, it can estimate sort of your tissue responses to the electrical current. With the general idea that tissues like muscle that have more water,

45:16
will conduct that electrical current more easily than tissues like fat. Now, this is a valid technology in some settings. We have some bioimpedance devices in the lab that cost $20,000 or more. And then we have these at-home body fat scales that you can get some of them for 15 to $30. So not that price is everything, but I just mentioned that too.

45:43
To clarify the point, this is a very broad technology. So some biopies devices, again, in the lab, if we have this nice device and we rigorously standardize our participants, we can get really good useful data. If people are using these at home haphazardly or even carefully just because of the limitations of these cheaper technologies, the numbers they're getting may not be particularly accurate. So...

46:07
Our lab actually conducted a study a few years ago that included, I believe, 15 different bioimpedance devices, including about a dozen at-home body fat scales. So this is published by Madeline Siedler, one of my doctoral students, is the first author on this. We also kind of have a lay-friendly write-up. But one of the main things we were looking at here was the reliability of these devices, so how consistent the measurements were they produced, as well as the validity.

46:35
and the validity over time. So how well you could track changes in body composition. And there were some devices that performed better than we expected, but the majority of these devices have relatively large errors, even in controlled settings. So if you're a listener and you have one of these devices at home, you would of course want these controlled settings. And that would typically mean assessing in the morning, after an overnight fast, you've voided your bladder, you're in the same minimal or no clothing.

47:05
everything has been essentially standardized. You're doing it the same way every time you step on. Even if you're doing that, which is best case scenario, there is quite a bit of noise in the measurement. If you want this to be demonstrated, try measuring every morning for a week. So every morning, you know, be fasted, rested, everything the same, you step on the scale, and just look at how much those values vary in a week. Even without doing formal statistical analysis, you can get a sense of how much change there is in the number you're receiving.

47:34
over a very short period of time where you're not having a true measurable change in body fat. So this is kind of a quick and dirty research experiment I'm describing for people to do. Say you saw that over the course of a week when you're not changing anything with your lifestyle and so on, you saw this number varying by say a percent. Like say you had 25% the first day, but over the course of the week, it was up to 26% some days down to 24% some days.

48:01
You may see that again, when no real change is probably occurring, you may have a value that varies by say 2% total. Then I would recommend if you are implementing some lifestyle change or wanting to track this, let quite a bit of time elapse. You don't want to be actually doing this every day. That's just for the point of showing you the error. Whether this is a month, a couple of months, a year, whatever it is, then you can assess again ideally maybe a couple of mornings in a row and averaging those assessments.

48:30
And if your change is larger than some of that variability you saw just within a week, then you can feel a little bit more confident, not entirely confident, but a little bit more confident that you might have seen a real change. Conversely, if this is six months later and you step on the scale, it says 25.5% body fat. Did you actually increase from the very first measurement you got of 25%? Probably not. Half a percent, as you saw, was well within just the normal variability of the scale. So I apologize, Vicky. I've gone on quite the tangent here about telling people to do their own experiments

49:00
But yeah, so I would say important to realize is any method, even if you go to a research laboratory and get a DEXA scan done or something like that, there's some error involved. So for any time you're trying to see if your body composition has changed, you should remember that general principle. Even if you don't have the exact numbers in terms of the percent error of a device, just realize that very small changes are unlikely to be real because just because of the inherent error.

49:28
And I'll pause there to see what follow-up discussion you want to have. I know. This is great. And so if people are interested in using that number as a bit of a measure alongside whatever else they're tracking, so we're really looking for a trend over time is of hopefully down because they're interested in losing body fat and to measure maybe once a month to track that.

49:56
in addition to the other markers and then they can be sort of confident as long as it's dropped enough and it's sort of outside of that era that they've already established. Yes, I think that's reasonable. And I would even say if you are doing a monthly assessment, I would do it maybe on two days in a row and average those. Cool. Because there's some random error that would be there at one assessment that if you average to it helps reduce some of that random error. Yeah. So even if you're tracking every month or every two months, I would do it a couple mornings in a row under the same...

50:25
standardized conditions and then average those two values to have the one value that you'll actually use and interpret. So that's another way you can help reduce a little bit of the noise of some of these consumer devices. And then I'd certainly recommend not only interpreting the body fat percentage. So it would take body mass as well. It's not perfect, but it is informative. So body mass, maybe something simple like circumference measurements, a waist circumference, hip circumference.

50:53
depending on what type of training someone's doing and what their goals are. Limb circumferences, say upper arm and thigh could be relevant, say to someone trying to gain muscle, for example. Those would be other assessments you could take and you could form kind of a collective picture. So if you had a scenario where, you know, over a two-month period of time, someone saw that their body fat percentage went up, but their body mass is lower, their waist circumference is lower, say visually they feel like their clothes are fitting better, there might be multiple points

51:22
I think I've actually lost some body fat. So I'm not going to put too much weight in this kind of strange bioimpedance result. So I would not get into this scenario where for one of these at home body fat scales where it's the only metric you're looking at. Just because again, even under the best case of standardization, averaging a couple of measurements, all these things, there's still enough error that you should be eternally a little bit skeptical of the results you're seeing. Yeah, that's great. And what about for people who use...

51:51
in body comes to mind. The local gym does body scans and they might do them once every six months. It's more than just stepping on a scale. You've got a handhold one as well. In fact, I used to have just a handhold one in the clinic. Are they more reliable because you've got more touch points with that machine or not really? If everything else was equal, then yes. These normal at home bifat scales you step on,

52:20
it is creating kind of electrical circuit through your body that's primarily running through your legs. So my confidence that these electrical currents are going all the way out to your arms and back down to just these contact electrodes on your feet is very low. So what you're describing is true that if you have electrodes on your hands and feet, there is more of the body that's being seen, so to speak, by the electrical currents. Yeah, InBody has some nice devices. They actually now have a...

52:47
kind of high-end consumer grade device. It's about $350. So expensive, but not thousands or tens of thousands of dollars like the ones that might be at gyms. If you do have access to a nicer piece of equipment, say at a gym, the main thing you'd want to be certain of is that you've standardized appropriately. So ideally you go first thing in the morning. This is before you've worked out. Again, you've voided your bladder. You've done all the things that I just recommended doing at home.

53:15
Because we've done studies on the InBody 770, which is a nice device and often the one that might be at gyms and so on. And we've seen things as simple as drinking water, just like a bottle of water can pretty dramatically affect your estimates and not always in the way you think. So in this one trial we did, we brought individuals in. They were fasted, rested, followed all these protocols we had prescribed. We assessed them on the InBody.

53:41
And then in one condition, they did nothing. They just rest in our lab and we continued to assess them every about 10 minutes for an hour. And in the other condition, they consumed water that would be one or two bottles of water is relative to body mass. And what we saw is because this, the InBody device has a scale integrated, it immediately detected the increase in body mass from drinking water, but it didn't actually change the bioelectrical currents, what was detected.

54:10
So what that meant is there was an automatic increase in fat mass. So we saw a, I think it was around 1.5% on average, increase in body fat percentage, just from someone drinking water, because it had increased their weight, but it was not yet detectable to the currents. So something as simple as that, like how much water you drink on your way to the gym to be assessed could influence your results. So if you are gonna use something like that, biopians again is a pretty sensitive technology.

54:36
you just have to be very meticulous about standardizing everything so that you have higher quality data. Yeah. And meal timing the night before, does that, is there a recommendation there, Grant? The night before, typically one of the reasons we assess in the morning is that overnight period of rest, hopefully sleep, normalizes a lot of factors. So we would normally say a minimum of eight hours of fasting before an assessment.

55:02
Again, as long as this is consistent and at least eight hours, that would be ideal. The exact timing if you ate at 7 p.m. or 8 p.m. the night before shouldn't be too impactful. Now I would recommend following your normal routine, so to speak, the day before and particularly the night before. So if the night prior to one assessment you had a feast and the night before another assessment you ate very lightly.

55:28
you could have larger differences in things like GI contents and things that might cause some artificial variation in your weight or even other things related to say fluid retention and so on. But I'd say in general, as long as you have that overnight fasting period and control your fluid intake, like the same fluid intake or no fluid intake the morning of, that'd be kind of the level of standardization that I would recommend. Yeah, nice. And what about hard training?

55:58
a marathon training run the day before, is that going to impact on the reading the next day? That's outside of the hydration aspect. So I've sufficiently rehydrated and stuff like that, but muscle damage or anything? It could. Typically, when we're performing these research studies with all these methods, we ask individuals to not perform any

56:25
moderate or vigorous intensity physical activity or purposeful exercise the calendar day prior. So often we'll say it's a 24 hour abstention, but it really ends up being sort of 36 hours because they have two overnight periods and a whole day prior. Now, depending on how frequently you're assessing, that may or may not be possible. But if you're talking about the scenario where there's the in body of the gym and you're assessing every six months, I would recommend, you know, ideally you would take a rest day prior or maybe light training.

56:52
the morning prior, so you have about 24 hours of rest. My suspicion is training status would play a role here. So if you're very highly trained and you go out for a long run the day before, but that's not, you know, it's a challenge, I'm sure, because you're pushing yourself, but it's not, you know, challenge your body the same way as someone who is less trained. My guess is that it would cause less error in the technique. But again, if you are doing one of these assessments, I recommend erring on the side of caution,

57:22
biological error, kind of noise in your body that could influence the measurement negatively. Yeah, nice. And Grant, finally, what is a healthy body fat percentage, actually? I see a lot of different numbers as the high-end cutoffs and people freak out when they're like 28%, but then I see 28% healthy. Do you have limits or cutoffs? What values do you use?

57:51
To be honest, I don't typically because it's very much method specific and even down to the particular device. So even on DEXA, for example, there are reference values published for the different manufacturers of DEXA showing what the different percentiles would be and so on. If I were to give you those values for DEXA and someone has an at-home body fat scale, it's very likely they would be different even amongst the at-home body fat scales. For example, the study we conducted.

58:20
there were some that systematically overestimated everyone or underestimated everyone. So I typically de-emphasize general numbers that could be applied across methods because the methods vary so much in the actual values they give. So to me, it's probably more important to have a method that has been demonstrated to be able to track a change over time. And even though people like the numbers and they wanna know if their number is good or not.

58:46
It'd be ideal to focus on whether that number is changing in the direction you want or say being maintained how you want rather than finding some chart somewhere that tells you this is good body fat percentage. And again, there are other metrics. Body fat percentage can be useful in some settings, but there are other metrics, say like circumferences or raw skin fold thicknesses. Metrics that would tell you some of the same information. Am I losing fat, for example, or am I likely losing fat? If I'm seeing...

59:15
my weight decrease and my waist circumference decrease. And I know based on my fat patterning, that that's a site where I tend to gain or lose fat. Things like that would tell you the same feedback without the fixation necessarily on that body fat percentage number. So I recognize I didn't answer your question because I usually try not to give out. If we're down to the specific method and I knew a lot of details, then I feel more comfortable providing it. But I hesitate to give information that then will be applied in a way that could.

59:44
be negative for someone. I know that was such an awesome non-answer actually Grant. Thank you. And then finally, if someone had all the money and all the resources and access, what would be the gold standard for measuring body composition actually? So currently for total body composition, and I won't go into too much detail, but what we call the molecular level. So all the different molecular parts of your body like fat.

01:00:13
protein, water, and so on. The gold standard is called a multi-compartment model. And this is where you split all body mass up into three or more compartments. This can go up to six compartments. But this is accomplished by assessing someone with multiple different individual techniques. So, for example, in our lab, we would perform a DEXA, which is dual energy x-ray absorbed geometry, scan on someone to get their bone mineral content. We perform...

01:00:42
Bod Pod to get an estimate of their body volume. We'd perform either a bioimpedance or dilution technique to get their body water. And we get a calibrated body mass. And we plug all those into an equation that would take these different components into account. And we could get a body fat percentage, but we've considered a lot more factors than any individual single method does.

01:01:11
these relatively inaccessible options. If you were interested specifically in like skeletal muscle and adipose tissue as tissues rather than molecules, like I was mentioning, then something like whole body magnetic resonance imaging would be what we do. And it's relatively inaccessible even in research. We're hoping to add that into our protocols this upcoming year, but that's another method. Again, looking at the body in a little bit different way, but another would be considered a gold standard method. Yeah.

01:01:40
Okay, that's awesome. Thank you, Grant. And you're right, they're not necessarily accessible, but it's good for people to be aware of it. But then also, I mean, how you've described how best to use the data that we've got is so helpful for people out there who are interested in this. Thank you so much for your time. Where can people find you and your research? Obviously, I'll pop it in the show notes. Yes. So,

01:02:08
I do share about our research on social media, mostly on Instagram and my handle there is grant underscore Tinsley underscore PhD. I'm also on Twitter and I'll share updates there as well. And then I have a personal website, which is just granttinsley.com where I have links to my research, some information about my research lab and other activities. That is awesome. And you have such a broad.

01:02:31
sort of research interest from all of the publications I've seen. Like this is like two areas, but there are so many other things there, which is super interesting. Grant, thanks so much. I really appreciate your time. Absolutely. Thank you for having me on. I enjoyed the chat.

01:02:58
Alrighty then, hopefully this just betters your understanding of the importance you might place on your bathroom scales and what they tell you, but also where you could go to get better body composition measurements and ones which are more reliable potentially than what you have on your bathroom scales. Next week, we have my mate and your mate, obviously.

01:03:21
Dr. Cliff Harvey back on the show, we discussed functional testing, which is something we've sort of talked around, but not really devoted an episode to. So Cliff and I have a really good discussion on it, and we don't agree on everything, which I think is also really good, because it just means that you get a much more broader perspective, I suppose, on the different functional tests that are out there, and where potentially you might want to spend your money or not. So that is next week on the podcast.

01:03:49
I will also just like to highlight that it's Black Friday this weekend and as per last year I will be running a Black Friday sale so keep an eye out on that. In the meantime catch me over on Instagram, Twitter and threads @mikkiwilliden, on Facebook @mikkiWillidenNutrition and also at my website mikkiwilliden.com. Alright team you have a great week, see you later.