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Hey everyone, it's Mikki here. You're listening to Mini Mikkipedia on a Monday. And today I want to chat about something I see a lot in my clinical practice. And honestly, I think a lot of you listening might recognize it in your own routine, just because of how prolific I feel it is. It's about short eating windows, time restricted eating, and why for lot of active people, especially women trying to lose body fat, the approach might actually be making things harder.

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and not easier. And I want to be really clear from the outset. I'm not saying that time restricted eating is bad at all. I'm an advocate for it actually. And there is research showing that when utilized in combination with resistance training, it is beneficial from a body composition perspective. And we know it's a legitimate dietary strategy that can work really well for some people. But what I do want to do today is unpack why it doesn't always do what people expect it to.

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And more importantly, what the research actually tells us about this interaction between restricted eating windows, exercise and appetite. Because sometimes when you layer those things together, which is exactly what a lot of my clients are doing, you sometimes get outcomes that are really counterproductive. So the idea behind time restricted eating or TRE is simple and intuitive. You compress your food intake into a shorter window.

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usually somewhere between 6 and 10 hours, although I know some people do OMAD one meal a day where everything is stuffed into two hours and you fast the rest of the time. The logic goes the fewer hours to eat means less food is consumed, which means a calorie deficit, which means fat loss, which is pretty straightforward, right? Except this isn't what the research consistently shows. Now, one of the most well-known trials in this space is the TREAT study.

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that is the time restricted eating randomized clinical trial led by Lowe and colleagues published in JAMA Internal Medicine. This is a 12 week randomized control trial, as the name suggests, in adults with overweight and obesity. And participants were assigned to either an eight hour eating window, eating between noon and eight, or a standard three meals per day pattern, no eating window required. Importantly, there was no calorie prescription, eat to satiety.

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They were not told how much to eat, they were just told when to eat, which makes us a really valuable real world study. The time restricted eating group lost a small amount of weight, about 0.94 kilograms over 12 weeks, which even if we consider the fact that that is not a significant amount of weight for people with overweight and obesity in the first place, it was not significantly different from the control group. There was no meaningful difference in estimated energy intake between the two groups.

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So people eating in a shorter window were not eating fewer calories. And here's the part that really stands out. And this is something I think doesn't get enough attention. In a subset analysis of an in-person cohort, about 65 % of the weight that was lost in the TRE group was lean mass. That includes muscle. It's not just muscle, but it includes muscle. Only about a third of what they lost was fat. Now, normally in a diet intervention, you'd expect lean mass to account for maybe 20 or 30%,

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even up to 40 % of total weight loss, 65 % is way above that. And Ethan Weiss, who I've had on my computer podcast before, he's one of the lead investigators, he'd actually said that he'd been practicing 16A himself and recommending it to patients. But after seeing results like that, the prescription of this version of time restricted eating was not a very effective weight loss strategy. So right from this study,

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We can establish an important baseline. Simply restricting when you eat without any attention to what or how much you eat does not reliably reduce calorie intake. And when it does produce weight loss, the composition of that weight loss may be problematic. But this is just one study. I will say that. And what about timing? Doesn't eating earlier help? There is some evidence that earlier eating windows do have some metabolic advantages. But again, there are some really important caveats.

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The key study I'm thinking about is one from Sutton et al. published in Cell Metabolism in around 2018. This was the first controlled feeding trial of what they called early time restricted feeding or E, little e, TRF. They took men with prediabetes and they had them eat within a six hour window with their last meal before 3 p.m. Then they compared that against a 12 hour eating window. This was a crossover design. So everybody did both conditions over five weeks each.

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which was great. Everyone effectively was their own control. And the results were impressive. The early eating window group showed improved insulin sensitivity, improved beta cell responsiveness, super important from glucose perspective, lower blood pressure, reduced oxidative stress and lower appetite ratings, all without any weight loss. And that part is critical. There was no weight loss because this was a controlled feeding study. They were not in a calorie deficit.

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were given enough food to maintain their body weight. The researchers specifically designed it this way because they wanted to test whether the metabolic benefits of intermittent fasting exist independent of weight loss. And they do. Eating in alignment with your circadian rhythms, front loading your intake earlier in the day when insulin sensitivity and the thermic effect of food are both higher, does appear to offer genuine metabolic advantages. The circadian

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system upregulates glucose, lipid and energy metabolism in the morning and down regulates them in the evening. So eating with that rhythm rather than against it does make physiological sense. But here's the nuance that I don't want you to miss. When calories are controlled, earlier eating does show benefit. When calories aren't controlled, which is how real people eat in the real world, the picture is much less clear. The Sutton study tells us about the potential of eating earlier. It doesn't tell us what people

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actually do when they say only eat between 8 and 2 p.m. because most people's lives and more importantly most people's appetite biology don't cooperate with that instruction. our physiology might favor early eating but behavior will always determine outcomes and this is a really important distinction. So let's bring exercise into this picture because this is where things really do get relevant for a lot of you. A comprehensive review by Blundell and colleagues

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Published in obesity reviews in 2015 looked at the relationship between exercise and appetite control. What they found is that exercise has what they describe as a dual effect on hunger. On one hand, exercise increases fasting hunger. That is, your baseline hunger signal goes up. On the other hand, exercise improves postprandial satiety, meaning that after you eat, you feel fuller for longer and you're more responsive to the signals from the food that you've consumed.

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I've talked before about how very sedentary people often miss the effect of exercise on the food that they eat and how it can help regulate their appetite. This is essentially what Blundell and colleagues were referring to. In theory, these two things could balance each other out. In many people, they do. However, compensation varies enormously from person to person. Some individuals barely compensated all, but they exercise.

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They burn extra energy and their food intake doesn't change much. Others partially compensate and some people overcompensate. They eat back more than the energy they expended. Blunders Group has done extensive work looking at why this variability exists. And one of the key insights is that it comes down to the relative strength of tonic versus episodic appetite signals. So tonic signals are the background sustained drives, things like your resting metabolic rate, your fat free mass and your leptin levels.

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and episodic signals are the meal by meal fluctuations, ghrelin rising before a meal, gut peptides like CCK, GLP-1 and PYY responding to food intake. Exercise influences all of these. It affects ghrelin, which is our hunger hormone. It affects gut peptides like CCK and GLP-1 and PYY. It affects how your brain processes reward signals from food, and it can shift the balance between wanting high fat or high sugar foods

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versus these energy dense options. The point is, the relationship between exercise and food intake is not a simple one-to-one energy equation. It's a complex physiological interaction with massive individual differences. And this is where it becomes really relevant to what we've been discussing. When you exercise, especially in the morning, and then delay eating for hours into a compressed window, you're essentially amplifying the hunger side of that dual effect

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without giving the satiety side any opportunity to do its job. You've trained fasted, you're driving ghrelin and neuropeptide way up, increasing reward-driven motivation for food, and then sitting with that mounting hunger pressure for hours until your eating window opens. And by the time you eat, it's not a calm, measured, satiating meal. It's a biologically primed feeding response. In that context, overconsumption becomes a...

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predictable physiological outcome and it's much more likely. So let me describe a pattern I see clinically because I think a lot of you are going to recognize this. Let's say you have a woman, she's in her 40s or early 50s, she's active, always has been, she might run, cycle or do some kind of gym based training in the morning. And she's been told or she's picked up from social media or a book that a shorter eating window is a good strategy for fat loss.

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She might not have had to have thought about this until she's hit this age, but here we are. So she trains at six or seven a.m., delays eating until noon or even later, and then she has her meals, say, between one and eight p.m. She feels like she's being disciplined, and she is. She's training hard, she's fasting through the morning, she's ticking all these boxes, but the scale isn't moving, or it's moving very slowly. Body composition, importantly, isn't changing, and she can't figure out why.

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And when we track what's actually happening, the answer is almost always the same. Within that compressed eating window, she's consuming just as many calories, sometimes more, than she would if she had spread her meals across a longer window. The meals are bigger, they're more energy dense, they're eaten faster, or she's grazing a lot more. She's not just consuming meals, she's having those in-between times to grab things mindlessly from the pantry or the fridge or that sitting on her desk.

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And the hunger signals driving those meals are so strong that portion control goes out the window. There are some less obvious but still relevant mechanisms at play here. When people under-fuel early in the day, particularly after exercise, spontaneous physical activity can drop. That's your non-exercise activity thermogenesis, or NET. The fidgeting, the walking around, the stairs you take instead of the lift. It's a small reduction, but it's meaningful. And over time, it chips away at total daily energy expenditure.

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There's also a cortisol consideration. Cortisol is going to be higher in the morning anyway. It's what gives us our get up and go. And morning training plus continued fasting may keep cortisol elevated for longer than it otherwise would be. Now, cortisol alone is not a fat storage switch at all. That is an oversimplification. But sustained cortisol elevation can increase appetite later in the day, particularly for highly palatable, energy dense foods.

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It biases your food choices in exactly the wrong direction. And then there's glycogen depletion. Not necessarily muscle glycogen as it takes a while to of deplete over time. But if you've trained in the morning and haven't eaten, then you're further impacting your liver glycogen because that's already depleted overnight. Your body has a drive to restore that glycogen and that drive might manifest as a preference for carbohydrate rich, highly palatable foods later in the day.

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And this isn't your body saying store fat, it's your body saying you're behind, fix it. And for some people, they fix it pretty aggressively. There is no strong evidence that delaying food after morning exercise sends a direct acute signal to store fat. So I'm not saying that. The idea of this fat storage mode is not supported by the literature. Your body isn't flipping this metabolic switch because you didn't eat within 30 minutes of training.

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What the evidence does support though is that the combination of an early energy expenditure plus delayed intake plus compressed feeding sets up a behavioral pattern that increases the likelihood of overeating. So the body isn't consuming fat in that moment, it's driving behavior that leads to a higher intake later. And this is what the research consistently shows across multiple lines of evidence. Time restricted eating does not consistently reduce calorie intake in free living humans. That's the TREAT trial.

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When TRE does produce weight loss, it appears to be primarily through passive calorie reduction, not through some unique metabolic pathway. There was another trial from Gebel, a pilot study from 2018, which took obese adults eating in an 8-hour window and found that they'd lost 2.6 % of body weight over 12 weeks, so significantly more, with a corresponding reduction in energy intake of about 341 calories per day.

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There was nothing magical though about that particular window, but for these individuals, eating within that window happened to result in eating less. Some metabolic benefits of eating early do appear to exist independently of weight loss. That's the Sutton data. Those studies control calories. When you create a big gap between exercise and eating, appetite often rebounds and some people overshoot. That's a blundered work on exercise and appetite compensation. So,

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Intake is highly variable, appetite is dynamic, and behavior drives outcomes. So what can we do with all of this? So here's some practical applications. First, if you're training in the morning and your goal is fat loss, eat something after your session. Even if it's not before, eat after. Doesn't have to be a huge meal. Make it a protein rich option, like some eggs with egg whites or a protein shake or something like that. And that'll blunt the rising ghrelin.

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Start the satiety cascade and set you up for a more controlled eating later in the day. Delaying that first meal for hours after training is not giving you a metabolic advantage. It's giving you a hunger disadvantage. And protein is the most metabolically favorable nutrient. Pop some carbs in there if you've trained hard. And second, if you are going to use a shorter eating window, match it to your actual life and your actual hunger patterns. If you trained early, a later eating window makes no sense.

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you're creating the biggest energy gap right when your appetite biology is most primed to push back. If you want the circadian benefits, the Sutton study demonstrated eating earlier in the day, not later, is where the physiology points. But for many of us, it's just not a practical solution in this modern everyday life we exist. Third, pay attention to the composition of your meals within whatever eating window you choose. One of the underappreciated findings in the TRE literature,

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is that when people compress their eating, protein intake often drops. And that's a problem, especially in perimenopause, when muscle preservation and bone is already an uphill battle. If you're going to eat within a shorter window, you need to be even more intentional about hitting your protein targets. And fourth, watch for the compensation pattern. If you find that after your morning training and extended fast, your evening meals are large, energy dense, and feel hard to control,

16:00
That's your appetite biology doing exactly what the research predicts it will do. And the solution isn't to try harder, fast longer, train harder, et cetera. It is to change the setup, distribute your energy intake in a way that works with your biology and not against it. And fifth, remember that time restricted eating is a tool. It's not a rule. It works for some people and it works best for people with naturally low appetites, structured habits.

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in moderate activity levels does tend to backfire for highly active people, people already pushing a deficit and people whose physiology is prone to strong compensatory hunger responses. So just know yourself and know which category you fall into. In closing then, it really does come down to the behavioral outcomes of what occurs when you restrict your food within a compressed window rather than what the research tells us about some of these benefits. Because the behavioral elements, which

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are actually driven by real measurable changes in appetite hormones and hunger signaling, you can actually do something about that. So it's not your metabolism working against you. You just need to find a way to sort of work within the scope of what your appetite and what your hunger allows you to do. So if your current approach involves training fasted, fasting through the morning, then eating in a compressed window, but the results aren't matching your effort,

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This could be the piece you're missing. You want to redistribute those meals, front load those calories, feed the training, and then just see what happens from there. And give it a few weeks, because I know many people who train, fasted, and don't eat across the morning don't feel particularly hungry. But that is trainable. You can train yourself to want breakfast in the morning. Anyway, thanks guys. That's what I've got for you. I would love to hear your experiences. Hit me up. I'm on Instagram, threads and x @mikkiwilliden.

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Facebook @mikkiwillidenNutrition. Head to my website, mikkiwillidne.com. Scroll down to the bottom, pop your name in there to sign up for my weekly email. All right, team, you have the best week. See you later.