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Hey everyone, Mikki here. You're listening to a mini-mikkipedia, the first one of 2026. And today we're tackling something I see constantly in my practice and with members who are worried about this kind of thing. People who are doing everything right on paper, tracking their calories, hitting the gym regularly, eating a good nourishing diet and yet they're gaining body fat.

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particularly around their midsection. And when I dig into their lives, there's one common denominator, chronic unrelenting stress. So the science behind stress-induced fat gain is pretty robust, well-established, and frankly, could be kind of terrifying when you understand the mechanisms at play. This is not woo-woo. This is endocrinology, metabolic physiology, and cellular biology showing us very clearly

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that you can be in a calorie deficit on paper and still be storing body fat because of what stress hormones are doing to your metabolism. So as we embark in 2026, I want to make the case that stress management can no longer be this optional nice to have that we tack onto the end of our health protocols. It needs to be right up there with nutrition and exercise as a non-negotiable pillar of metabolic health. Because without addressing chronic stress, diet and exercise alone simply won't cut it for most people.

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which is one of the reasons why I talk about this all of the time when I talk about fat loss and I talk about mindset and I talk about exercise and I talk about calories. It is all with the stress management piece in mind. People don't love that though because they don't love the idea of addressing something that isn't ultimately within their control. mean, stress management is. This is the thing.

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People perceive stress in a different ways. And for some people who do have busy lives, busy jobs, relationships which are tricky, they feel a little bit like that control is not within their reach. But there are things that you can do about it. I wanna walk you through exactly what that stress physiology looks like. The specific mechanisms by which stress hormones, particularly cortisol, not only make us store fat, but...

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preferentially direct that fat storage to our abdomen region, creating visceral adiposity that's metabolically dangerous. We'll talk about fuel partitioning, why stressed bodies burn muscle instead of fat, even when you're under eating, and why the simple calories in, calories out model falls apart when cortisol is chronically elevated. I will very clearly state this isn't that the energy balance model of sort of dieting is not that

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underlying physiology, of course it is. But what stress does is it impacts on a range of levels which stops it from being the simple calories in calories out. First let's establish a key player here. That's clearly cortisol. Cortisol is our primary stress hormone released from the adrenal glands in response to physical or psychological stress. Now, as you know, cortisol isn't inherently bad. It's actually essential for survival.

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And in acute situations, cortisol mobilizes energy, sharpens focus, and helps us respond to threats. It's even anti-inflammatory. The problem isn't cortisol itself. It's that chronic elevation of cortisol that wrecks metabolic havoc. And when I say chronic elevation, I'm talking about the modern reality for many people. Work stress that never switches off, financial pressure, relationship difficulties, chronic sleep deprivation, overtraining without adequate recovery.

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constant exposure to inflammatory foods, even the stress of extreme calorie restriction itself. All of these keep cortisol elevated day after day, week after week. And this is when it can get interesting from a fat storage perspective. Cortisol doesn't just make you store more fat, it has a preferential target, and that is visceral fat. That's fat that's stored deep in your abdomen cavity, surrounding your organs, as opposed to subcutaneous fat, which sits just under your skin.

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And there is a very specific reason why cortisol preferentially stored in visceral fat tissue. First is receptor density. Visceral adipose tissue often has a higher concentration of glucocorticoid receptors compared to subcutaneous fat. These are receptors that bind cortisol. So when cortisol is circulating in your bloodstream, it preferentially acts on visceral fat cells because that's where there are the most binding sites.

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Think about it that visceral fat has more doors for cortisol to walk through. Second is the enzyme 11-beta-HSD1. This is crucial. So visceral adipose tissue can have a higher activity of an enzyme called 11-beta-hydroxysteroid dehydrogenase type 1. What this enzyme does is convert inactive cortisol into active cortisol locally within the fat tissue itself.

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So even if your blood cortisol levels aren't dramatically elevated, the visceral fat tissue may be creating its own local cortisol environment, amplifying the effects. So this is why some people can have normal cortisol in a blood test, but still be experiencing the metabolic effects of cortisol excess in their adipose tissue. And I will say that cortisol measured in the bloodstream might only be measuring about 3 % of cortisol that might be.

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within your system. A third reason why cortisol loves visceral fat tissue is to do with lipoprotein lipase upregulation. Cortisol can increase the activity of an enzyme called lipoprotein lipase, LPL, specifically in abdominal adipocytes, which are fat cells. LPL is essentially the gatekeeper for fat storage. Breaks down triglycerides from your bloodstream so they can be taken up and stored into fat cells. When cortisol upregulates LPL in visceral fat, it literally

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opens the gates for more fat to be stored in that tissue. And fourth, you've got adipocyte differentiation. Cortisol promotes the differentiation of pre-adipocytes. So these are like little baby fat cells. And to mature adipocytes, particularly in the abdomen region, so you're not just filling up existing cells, you may be creating more fat storage capacity in your belly. Now, there's one more critical piece to this puzzle, and it's something called the portal vein hypothesis.

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Visceral fat is metabolically different from subcutaneous fat, partly because of its anatomical location. The visceral fat drains directly into the portal vein, exposing the liver to higher concentration of free fatty acids and inflammatory mediators. This may promote hepatic insulin resistance and steatosis. So this can create a vicious cycle. Stress elevates cortisol. Cortisol preferentially stores fat in the visceral depot. That visceral fat releases inflammatory cytokines.

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and free fatty acids directly to the liver, the liver can become insulin resistant and metabolically dysfunctional, which further dysregulates glucose and lipid metabolism, creating more metabolic stress, which keeps cortisol elevated. Round and round we go. So this is why this little adipose is so strongly associated with metabolic syndrome, type 2 diabetes, cardiovascular disease, and non-alcoholic fatty liver disease, or what is more...

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what is clinically known now as metabolic associated fatty liver disease. It's not just about aesthetics, which I know is one of the things that we're so concerned about. It's about that metabolic danger that this particular fat depot represents. And note that this can all happen even when calories are lower and on paper, low enough to be in a calorie deficit. So since we've established that cortisol preferentially stores fat in your abdomen, something else to talk about

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is fuel partitioning, because this is where the calories come into play. Fuel partitioning refers to how your body decides what to do with incoming nutrients and stored energy. Where do the calories go? Do they get burned for energy? Stored as glycogen and muscles? Converted to fat? Used to build muscle tissue? Your hormone environment is a traffic cop directing these decisions. In a healthy metabolic state where stress is appropriate, fuel partitioning generally works in your favor.

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After a meal, insulin rises, glucose goes into the muscle cells to replenish glycogen, amino acids support muscle protein synthesis. And yes, some energy might be stored as fat, but you'll also oxidize that fat during periods between meals when insulin drops. So there's a nice balance. And when it comes to gaining fat, it really is that flux of fat that's being stored in tissue versus fat that's being used for energy. However,

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And this is where chronic cortisol elevation can rewrite these rules. Firstly, cortisol promotes gluconeogenesis. That's the creation of glucose from non-carbohydrate sources, primarily amino acids. This is a normal adaptive response to stress. Cortisol signals that the body may need readily available glucose to respond to a perceived threat. Under conditions of chronic stress, especially when energy intake, recovery, sleep, or resistance training are insufficient,

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Cortisol increases muscle protein breakdown to supply those amino acids. Even with adequate protein intake, persistently elevated cortisol can shift the body towards using muscle tissue as a glucose source rather than preserving it. And this is metabolically expensive and counterproductive for fat loss. Muscle is your most metabolically active tissue. Losing it reduces resting energy expenditure and worsens insulin sensitivity, effectively shrinking your calorie burning engine

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or cortisol simultaneously pushes the body towards fat storage. Second, cortisol can create tissue-specific insulin resistance. So cortisol can impair that insulin signaling in skeletal muscle and the liver, making these tissues less responsive to insulin's glucose uptake signals. At the same time, adipose tissue, particularly visceral fat, tends to remain relatively insulin sensitive in comparison. Practically speaking, this means that when you eat carbs,

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Glucose is less efficiently taken up by the muscle for fuel or stored as glycogen. Instead, it's more likely to be diverted towards that fat storage, especially in the abdomen region. Cortisol isn't eliminating glucose used by muscle entirely, but it's biasing nutrient partitioning away from muscle and towards fat. And this is how someone can be under eating, losing muscle mass, and still accumulating fat mass at the same time. The scale may not change that much or may even drop.

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or the body composition quietly shifts in the wrong direction. Third, cortisol interferes with fat mobilization and oxidation. While acute cortisol can help mobilize fuel, chronically elevated cortisol has the opposite effect. Over time, it makes stored fat harder to access and burn. It blunts the normal lipolytic response to catecholamines like adrenaline and noradrenaline. These are hormones that would otherwise signal fat cells to release fatty acids for energy.

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Chronic cortisol exposure also promotes a hormonal environment where insulin remains elevated more often and insulin is strongly anti-lipolytic, i.e. strongly anti-fat burning. On top of this, prolonged stress and cortisol exposure can impair mitochondrial efficiency in skeletal muscle. Mitochondria is where fat oxidation occurs. When they are not functioning optimally, the body becomes less able to use fat as a fuel source.

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even when calorie intake is low, carbohydrate is restricted or training volume is high. To put together, chronic cortisol elevation doesn't just make fat loss harder, it actively shifts the body towards muscle loss, fat storage and metabolic inflexibility. So this isn't a failure of discipline or effort, it's a predictable physiological response to sustained stress, insufficient recovery and prolonged energy deficit. So.

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Let's chat specifically about why eating less can actually backfire when you're chronically stressed. The conventional wisdom is that you create a calorie deficit, you lose weight. And in a healthy metabolic state, this generally works pretty well, at least initially. But when chronic stress and caloric restriction combine, you create what I call a metabolic perfect storm. The reasons for this, first, caloric restriction itself is a stressor. When you reduce food intake significantly,

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especially if you're already lean or active, your body perceives this as a threat to survival. Your hypothalamic-perturatory-adrenal axis, which governs the stress response, can become elevated, cortisol rises. This is well documented in the research. So if you're already stressed from work, relationships,

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or overtraining and then you add on an aggressive calorie restriction, you're not reducing one stressor and replacing it with another, you're adding a stressor, you're stacking them and cortisol goes even higher. And with that, the body composition shift accelerates. As we discussed, cortisol promotes muscle catabolism to fuel gluconeogenesis. When you're under eating, especially if protein isn't adequate or you're in too steep of a deficit, the muscle loss accelerates.

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And remember, every bit of muscle you lose reduces your metabolic rate. Research suggests that muscle tissue burns approximately six calories per pound per day at rest, compared to about two calories per pound for fat tissue. My caveat here is that these numbers, you see them slightly different in different research papers, but the ratio is pretty much the same. So losing muscle and replacing it with fat, even if your total weight stays the same or goes down, reduces your calorie burn.

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Metabolic adaptation can intensify. So yes, this metabolic adaptation happens with any calorie deficit because your body is smart and reduces energy expenditure to match its intake. But research shows that metabolic adaptation is more pronounced when caloric restriction is combined with high stress. So you get a greater than expected drop in metabolic rate beyond what would be predicted by weight loss alone. Some research searches believe this is partly mediated by cortisol's effects on thyroid function.

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cortisol can reduce that conversion of T4 to active T3, which is your primary metabolic thyroid hormone. And of course, with this, this can all be reversed with appropriate calories. However, the metabolic adaptation is enhanced when you are stressed. Energy availability can also become critically low. This is something I do think about a lot with my endurance athletes and my perimenopause clients. Energy availability is the energy left over after exercise for all other body bodily functions.

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Things like immune function, bone remodeling, reproductive function, protein synthesis, cellular repair. It's calculated as energy intake minus energy expenditure relative to lean mass. And research suggests that energy availability that is chronically low, which it suggests below 30 calories per kg of fat-free mass per day, can start to cause physiological dysfunction.

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And whilst we can critique the actual value of energy availability, what is clear is that if this goes on for too long, then that relative energy deficiency syndrome can absolutely exist. If you're stressed and under eating, cortisol is creating a state where your body is wasting energy on unnecessary gluconeogenesis, storing energy as fat instead of making it available for cellular functions, and failing to efficiently produce energy from the food that you eat.

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So even if your calculated energy availability looks adequate on paper, your functional energy availability, the energy your body can actually access and use, is lower. There is also something which can be seen to do with the interaction of insulin and cortisol. When you are in a calorie deficit, your insulin levels may be low most of the time, which should theoretically support fat burning. But when cortisol keeps you in a catabolic state,

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preferentially breaking down muscle, when you do eat, even a moderate amount of carbohydrate can cause this exaggerated insulin response because your cells are so insulin resistant. That insulin spike can shut down any fat burning and promote fat storage. And because you are so insulin resistant, the nutrients may not replenish muscle glycogen effectively. So you end up with the worst of both worlds. This is one of the reasons why we see people who are insulin resistant

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if they're highly stressed, even if they have an appropriate carbohydrate intake. So isn't the carbohydrate intake in this instance, it's the stress that's keeping them there. And the last thing I want to mention about this calorie related stress response is hunger and cravings can also intensify. Cortisol affects appetite regulating hormones. It can increase ghrelin, which is our hunger hormone, and decrease leptin sensitivity, which is our satiety hormone. So if you're fighting

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against your own biology, dealing with intense hunger and cravings, which makes adherence to caloric restriction increasingly difficult. When you inevitably have a higher calorie day or meal, your body is primed to store those calories as fat. So this is often why I see better results when we increase calories slightly for the stressed clients, particularly protein and particularly around training.

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carbohydrate around training also actually. We focus on supporting energy availability, reducing the restriction stress, supporting muscle mass and addressing the cortisol issue through stress management techniques. The body composition improvements that follow aren't from creating a larger calorie deficit, they're from normalizing the hormone environment so that fuel partitioning works properly again. And this is one of the premises behind what Brandon de Cruz talks about with the work he does at priming his clients for fat loss.

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So they might come to him in a super stressed state and they may be carrying more body fat and lower muscle, but his go-to isn't to address the fat loss first, it's to address that stress state first to get their body primed to lose fat in a normal hormonal environment, which is really smart. So there's one last thing I wanna talk about and that's looking specifically at fat oxidation, which is our body's ability to burn stored fat for fuel.

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People often think if they're eating low carb, doing fasted cardio, or creating a calorie deficit, their body must be burning fat. And again, in a healthy metabolic state, it probably is. But chronic stress fundamentally impairs your fat burning machinery. Your mitochondria, which people like to call the cellular powerhouses, this is where fat oxidation occurs. Beta oxidation, the process of breaking down fatty acids to produce ATP energy, happens in the mitochondria.

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Chronic cortisol exposure can impair mitochondrial function through several pathways, including oxidative stress, damaging mitochondrial membranes and proteins, reduced mitochondrial biogenesis, so we don't get the same number of new mitochondria, and we can disrupt mitochondrial dynamics, so the balance between mitochondrial fusion and fission gets thrown off.

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So when your mitochondria aren't functioning optimally, your capacity to oxidize fat is compromised at the most fundamental cellular level. Could be doing everything right from a macronutrient perspective, but if your mitochondria aren't efficiently processing fatty acids, you won't burn fat effectively. You can also have an impaired catecholamine response. Under normal circumstances, catecholamines, are adrenaline noradrenaline, bind to

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beta androgenic receptors on fat cells and triglycolysis. This is a breakdown of stored triglycerides into free fatty acids and glycerol that can then be released into the bloodstream and burned for energy. Chronic cortisol exposure blunts this response. We don't fully understand these mechanisms, but there is some research to show that chronically elevated cortisol reduces the density of these beta adrenic receptors on our fat cells or adipocytes.

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and it can impair the signaling cascade that follows. So even when catecholamines are released, like during exercise or fasting, they can't effectively trigger the fat release from the adipose tissue. So this can be particularly frustrating for people who are doing a lot of HIIT workouts or other forms of exercise specifically designed to trigger catecholamine release, but the hormone signal that is there isn't being responded to by the fat cells. So all of this can result in metabolic

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inflexibility. A healthy metabolism is metabolically flexible. So it's our ability to efficiently switch between burning carbohydrates and burning fats, depending on availability and demand. Chronic stress creates metabolic inflexibility. So you get stuck primarily burning glucose or breaking down muscle for glucose when it's not available, and you lose the ability to efficiently switch to fat oxidation. And there is a paradox here with exercise, which I already mentioned.

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When people add more exercise to try to burn more fat, if cortisol is already elevated in their under eating, the additional exercise stress can make everything worse. Exercise acutely raises cortisol, which is normal and healthy, but if you're chronically stressed, not recovering adequately and under fueling, exercise can become another chronic stressor. Cortisol stays elevated longer post exercise, recovery is impaired,

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And instead of the exercise session promoting fat oxidation and metabolic health, it accelerates muscle catabolism, further impairs mitochondrial function and drives you deeper into metabolic dysfunction. So this is when we have this sort of over-training or under-recovering, people doing excessive exercise, people under-eating and under-sleeping, and their body composition can get progressively worse. So I've talked you through a bunch of mechanisms that hopefully

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drive home the message that you cannot optimize body composition, metabolic health or fat loss without addressing chronic stress. Diet and exercise alone will not cut it if cortisol is chronically elevated and may be contributing to the issue. And I want to be really clear about what I mean by stress management as well. Effective stress management needs to address stress at multiple levels, such as sleep. Sleep deprivation, as you know, is one of the most potent drivers of

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cortisol elevation. So chronic sleep restriction can keep cortisol elevated, impair insulin sensitivity, increase hunger hormones, and reduce impulse control around food. You simply cannot out-diet or out-exercise chronic sleep deprivation. Training volume and intensity must match recovery capacity. So if you're sleeping poorly, eating in a deficit, and dealing with high life stress, you cannot train like an athlete in a recovery phase with adequate nutrition.

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Your training needs to be titrated to your current stress load and recovery capacity. This might mean fewer HIIT sessions, more low intensity steady state work, more active rest days, or even switching to restorative practices like yoga or walking with strength work during particularly high stress periods. I know this feels counterintuitive when you're trying to lose fat, but I promise you, managing cortisol will give you better results than grinding yourself into the ground with exercise that your body can't recover from.

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we need nutrition to support energy availability. Aggressive calorie restriction during high stress periods is counterproductive. Focus on adequate protein to preserve muscle mass, aiming for 1.6 to 2.2 grams per kg of body weight, include sufficient carbohydrates around training to support performance and recovery, and appropriate amounts of dietary fat for hormone production in cell membrane health. Consider the nutrient timing as well. Avoid extended fasting.

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distribute your protein across the day, carbohydrates around training, and micronutrients are super important as well. Vegetables, fruits, maybe a broad-spectrum multivitamin. Address psychological stress directly. So this is where meditation, breath work, therapy, journaling, time and nature, social connection, and hobbies come in. The interventions that absolutely lower cortisol, and we see this in the research.

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And it doesn't have to be 90 minutes a day or even half an hour a day, finding something that suits you that you can do on a frequent basis, maybe more effective than three times a week meditation therapy that lasts for 90 minutes. You need to do something that you will actually do consistently. It might even be a 10 minute walk outside, regular phone calls with friends who make you laugh, writing down three things which you feel grateful for.

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anything that you can stick at and will generally move the needle. Two other things I want to very briefly mention, consider testing and targeted interventions. For some people, it's worth testing cortisol patterns. This could even be, I know this is a little bit contentious, but a Dutch test that also has salivary cortisol testing so we can look at cortisol patterns across the day, look at cortisol metabolites and see what might need targeting.

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This targeting may include adaptogens like ashwagandha and rhodiola. Don't always check, course, for contraindications and individual responses. It might mean some phosphatidylserine that can blank cortisol spikes. As always, the caveat of not overdoing these is important as per another Manimicapedia episode. Might be magnesium and vitamin C. But do know that supplements can support, but they cannot replace the foundational lifestyle interventions.

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You cannot supplement your whey out of sleep deprivation, overtraining, and under recovery. And think about waist circumference as a key metric. I want you to start paying attention to waist circumference as much as or more than scale weight. Measure at the narrowest point of your waist or at the level of your belly button consistently, first thing in the morning before eating.

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If it is increasing even while your weight is stable or decreasing, that's a red flag for visceral fat accumulation and may indicate cortisol driven fat storage. For a woman, a waist circumference over 80 centimeters and for a man over 92 centimeters starts to indicate metabolic concern in levels of visceral adiposity. So I know this has been a lot of science, but I think it's important to

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really understand what's happening in your body at a mechanistic level because it helps you to understand why the standard advice of eat less, move more fails so many people in a stressed place. If you take nothing else away from this, just note that stress management is not optional. It's not a cherry on top of your health protocol. The last thing that you address once a diet and exercise is in place might for most of you be the first place that you start. So as we head into 2026,

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make this a true priority. Protect your sleep like your life depends on it because it actually does. Match your training to your recovery capacity. Eat enough to support your energy availability. Find practices that generally reduce your psychological stress and do them consistently. Consider testing and assessing with a health practitioner like a naturopath if you suspect HPA access dysfunction. So there's a lot. I'd love to hear your thoughts. I'm over on Instagram threads and X.

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@mikkiwilliden. I'm at Facebook @mikkiwillidenNutrition or head to my website, mikkiwilliden.com, book a one-on-one call with me. All right team, have a great week.