Transcribed using AI Transcription, error may cocur. Contact Mikki for clarification

00:10
Hey everyone, it's Mikki here. You're listening to Mini Mikkipedia on a Monday. And today I want to chat about a newish study that was released in May this year in the Annals of Internal Medicine. And it was looking at a time-restricted feeding protocol versus a usual eating protocol. And the impact that it has on body weight as the primary outcome, and then also looking at glucose.

00:37
markers and insulin resistance. So I suppose in the scientific community there is, I mean, there's always debate around nutrition isn't there. And one of them is, you know, what is the best pattern for someone to eat in order to see the most improved outcomes? Like what is going to work best for most people? And with time restricted eating, which is a caloric intake that is restricted to specific times of the day.

01:05
It has been sort of touted as, and could well be, a promising intervention to address obesity and associated metabolic risk factors. And it's sort of termed chrono-nutrition because you are exploring not necessarily a change of intake, but a change in the timing of the intake. So in particular, timing of eating during the active period, so for us humans, that is the daytime.

01:32
which is also consistent with the circadian rhythms of our natural biology, it might actually improve metabolic outcomes. This is of course in comparison to an eating pattern of similar calories. You know, if you just consume a similar amount of calories or same amount of calories, regardless of what time you eat, is that going to be better, worse or the same than a time restricted eating protocol?

02:01
People out there believe that time-restricted eating actually has benefits over and above the caloric restriction it can provide. So oftentimes with time-restricted eating, what you are unintentionally doing is you're restricting the number of calories that is going in, and it is one of the most important levers of a fat loss protocol. So it's something that you can change that naturally reduces calories so people are able to lose weight.

02:28
seemingly effortlessly and with that weight loss improve other metabolic outcomes. There are people who are in the camp of, well it doesn't really matter, it is that in fact it's the calorie restriction that is doing the job there, so we can't say that this is to do with the time restricted eating and that eating window is actually just to do with the calories are being restricted. And then there are other people that are saying that actually timing of eating really does matter.

02:55
Eating in alignment with our circadian biology does matter, and that is what is providing that advantage there. And of course, you might say to yourself, haven't we done studies like this before? Don't we already know what the primary benefits are? And regardless of the time of day that is focused on, because time restricted eating falls into a number of patterns. It might be that you're an early time restricted eating. So you're eating between say 8 and 2pm.

03:24
or your late time restricted eating, which might be, you know, 12pm to 8pm and fasting through the morning, or you're some sort of combination of that. But regardless of the time of day that is being studied, prior trials of time restricted eating were either not actually eating studies. And what I mean by that is that they didn't really control for calories or control the food. They just controlled the window with which the participants were eating in, or the trials where they did control the

03:53
what they ate, there were substantial limitations, including a short duration of intervention, small sample sizes, or low retention rates. So people would drop out of the trials. So it really did limit and does limit what we can interpret from these studies. It is really difficult then to assess whether the prior results of time-restricted eating that you might know, whether we can really rely on those results and whether it was in fact that they were eating within a time-restricted window.

04:23
or it was actually due to other confounding factors other than the timing of food intake. So really the critical issue is whether there is a benefit of time restricted eating on weight results and metabolic outcomes from reducing the caloric intake or is it actually the eating window itself? So that is what this time restricted eating study sought to investigate. And I'll put a link to the abstract and the methods paper.

04:50
in the show notes so you can see the study that I'm referring to. So whilst they were looking at a weight outcome, they weren't necessarily looking at a weight loss study. They just wanted to know if we kept calories constant within both groups in the study, the intervention group that had a time restricted eating window or the usual eating pattern group where they ate across 16 hours, would they lose weight? So what they had to do was...

05:18
determined the baseline daily calorie need for each of the participants in the study and they randomized participants to each group, either the time-restricted eating group or the usual eating pattern group. The calorie level was then held constant throughout the intervention period to ensure that changes in weight and other outcomes were related to the timing of the eating and not changes in caloric intake. Now this is an extremely challenging study to run.

05:48
It is not only incredibly expensive. To control what people eat down to the calorie is, I would say, nigh on impossible, but it's very, very challenging. And the lab that did this study are also responsible for running other controlled eating studies such as the DASH trials, which were super popular back in, I'm gonna say the 90s actually, in early 2000s, because I remember they were being published around the time I was doing my masters. So what they had to do for each participant

06:17
an equation to estimate or determine their daily caloric requirements. And they use the Mifflin-Saint-Diore equation, which is quite, if I say accurate, I would say it's quite a popular equation to use. And it entails different equations for men and women. And they have variables in the equation such as age, height, and weight. So it doesn't necessarily account for muscle mass in that particular equation. What they then do is multiply.

06:45
the number of calories that have been calculated for that individual by an activity factor. And so the activity factor was determined using a questionnaire called IPAC short form, and that's the International Physical Activity Questionnaire. And people basically use that to establish an activity factor related to either whether or not you were sedentary.

07:13
you're moderately active or very active. So what happens, and I know this is quite convoluted, but you take your basal metabolic rate as determined by the Miflins-Saint-Gior and you times that number by 1.2 if you're sedentary, 1.4 for moderate activity, and 1.6 for very active. And I would say most people probably fall into the low to moderate activity group in the general population.

07:42
And the very active or highly active people might be people who are doing sort of endurance-based exercise. And in addition to controlling for calories and providing meals and snacks, and I'll outline what that looked like in a minute, the participants also wore something called an accelerometer, which actually just measures your energy expenditure and your physical activity. We obviously nowadays we have mini accelerometers.

08:07
sort of in our watches that can sort of determine that for us, but the ones used in the study were of very, you know, very well calibrated and highly sensitive to activity. So body weight was a primary outcome in the study and other secondary outcomes were changes in fasting glucose. They also wanted to look at insulin resistance, so they used a marker called HOMA-IR or homeostatic model assessment for insulin resistance.

08:36
They also wanted to look at glucose control across two hours. So they used the area under the curve of an oral glucose tolerance test. And then they also measured something called glycated albumin. Now, this is a marker of glucose management, much the same way that glycated hemoglobin or HbA1c is used. They just didn't use that in the study. And it seems that that was in part because there was an error as to what type of

09:05
blood they ended up taking in the study. So they should have taken sort of full blood off to be able to measure HbA1c, but they didn't in fact do that. So they instead used glycated albumin. So first of all, the two different patterns of eating was either the time-restricted eating or the usual diet pattern. Now the time-restricted eating was a 10-hour eating window between 8am and

09:33
6pm, which I know doesn't sound very short, but the participants were required to eat 80% of their calories before 1pm. So essentially this moved most of their calories to an early time restricted eating pattern. So breakfast they had to eat 40% of their calories, lunch they had to eat 40% of their calories, and then they had another 20% of their calories. 5% of that was used for a snack, and then 15% of calories.

10:02
was left for dinner. The usual eating pattern group, they had 16 hours to eat. So they could eat anytime between 8am and 12am. So they had an eight hour fasting window. However, their remit was having 50% of their calories being eaten at dinner time. So they were eating 20% of their calories at breakfast, 25% at lunch, had a 5% snack in there and

10:31
also had 50% of their calories coming in after 5pm. And they did that because that is what the literature tells us, that is how people eat. And if you think about how you might eat, often, I mean, like you listen to this podcast, you probably don't fall into the usual eating pattern group, but a lot of people really skimp on breakfast with like wheat bakes or toast or something like that. Then they might have a sandwich at lunch, maybe a piece of fruit if they're quote unquote healthy.

10:59
But oftentimes people don't have a ton of time during the day to get in the food, then they come home, they're starving, and that's when the biggest meal happens. The one other aspect of this, which I think is worth sharing, is that the participants had to sort of fall into the obese category when looking at body mass index. So they really wanted to look at people who had issues with blood sugar, who had issues with body weight.

11:26
because these were some of the things that they were looking to correct. Now, they did this for 12 weeks, and what the study found was that there was no difference in weight loss. And I know that you're thinking, hang on, Mickey, this wasn't a weight loss study. And you were right, but they wanted to see when they controlled for calories and nutrients, I didn't mention that, they also ensured that the micronutrient status of the diet was the same and the macronutrient.

11:54
status of the diets were the same, when they controlled for that, is there an effect of that eating window on weight? And there wasn't. So this tells you then that when calories are controlled and the same, it doesn't really make a difference in terms of the weight that was lost. Now, interestingly though, both groups did lose a little bit of weight. Like I believe it was around 2 kilos or 2.3 kilos.

12:22
each of the group, but there was no difference between the group. So with that amount of weight loss, that sort of tells you that the estimation of the energy expenditure as I described earlier was probably a little on the light side because they did lose a tiny little bit or potentially actually the people coming into the city were eating more a lot more. And so when they sort of moved and shifted closer to the maintenance calories, they ended up shedding a little bit of body fat, but there was no difference between the groups.

12:52
ultimately tells us from a weight loss perspective, any benefit of time restricted eating largely may come from the fact that it will naturally restrict your calories because when calories are controlled, it didn't matter when they were eating. And another interesting thing was that there wasn't a difference at the group level with markers such as the fasting glucose, the area under the curve for glucose, the glycated albumin,

13:21
and also HOMA-IR. So those blood sugar regulation markers they were also interested in were no different in the group. Again, this potentially suggests that under a controlled environment, it doesn't matter when you eat, it's not gonna make too much of a difference to your blood sugar markers. And I'm super interested in that aspect because previous studies, albeit limitations, there are limitations of those studies, would suggest that there is some

13:50
metabolic advantage to eating your calories within a window and having a longer period of time when you're not eating. But that's not what the study showed. And this is just one study, so we do need to be mindful of this. And it is a particular group of people as well, so how generalizable it is to other populations we don't know. But at that group level, there was no difference between the amount of weight that was lost or the fasting glucose markers. So really, what do you take from that?

14:20
I think importantly, it doesn't mean that time-restricted eating doesn't work. So please don't think that. And that's not what I think either. I think this just means that you just need to do what works for you. There is some people that really align well with a time-restricted eating pattern because it does allow them to control what they do on the food front without it being too much effort. Whereas if they were...

14:45
eating across all hours of the day, they might have to dial in more, how much they're eating at any particular time, to eat that same number of calories. So despite the fact this wasn't a weight loss study, I think we can still use this information in a positive way by thinking, well, if time-restricted eating only works because you restrict your calories, isn't that a bonus? You're restricting your calories. Time-restricted eating is the protocol for you. However...

15:12
If you are someone who really struggles to eat within say a 10 hour eating window or you know something else that's shorter like an eight hour eating window, this should give you confidence to know that it might not be the most important part. And I've always actually thought that, no, that's not true. Of late, I've evolved to understand, that's a better way of putting that, that in fact timing is not the most important thing. It's what you're eating that's more important.

15:42
And the study does lend itself well to reiterating that point. Because some people just can't fast. For whatever reason, they just feel hungry and they want to eat. So even if we're thinking about from a fat loss perspective, overall, it's the calorie deficit that is the most important. So whether or not you're eating that 1,800 calories across 10 hours or 15 hours, it's still only 1,800 calories. And if that's enough to get you in a deficit

16:11
lose fat, then you will still lose body fat. Now a critique of the paper that will likely come up and has come up is that these people weren't really eating in a short window because it was still a 10 hour window. Interestingly when the authors analyzed the actual timing of that eating window, it was 8.8 hours. So it was shorter than the 10 but not quite as short as the 8 or 6 that some people do like to do.

16:40
So that is one potential critique of the paper. So does this truly test the theory that time-restricted eating doesn't have this metabolic advantage? And I think, in fairness, I think that's a really good question, and I think it would be super interesting to run this whole study again, right, and do it so the actual time-restricted eating element was between 8 a.m. and say 1 or 2 p.m. It actually was.

17:08
quite a short window that would be very interesting to see. But until then, this is sort of the newest kid on the block, if you like, with intermittent fasting. So it's an interesting study to think of nonetheless. And if you've got any thoughts on it, because of course, you know, I'm just giving a bit of a brief overview of it. But if you've got some thoughts, I'd really love to hear them as well, obviously. So hit me up in my DMs over on Instagram @mikkiwilliden. I'm also on threads and Twitter at that same handle.

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or head to Facebook @mikkiwillidenNutrition, or go to my website, mikkiwilliden.com, and for a more nuanced discussion about how time-restricted eating could work for you or not, you could book a consult. All right, team, you have the best day. See you later.