How Does Stress Affect Appetite? Understanding Overeating and Appetite Suppression Due to Stress From a Recent Study

by | Dec 22, 2022 | Featured | 0 comments

If you’ve been following me for any length of time, you know how important it is to manage stress in client transformation. Stress manifests from many different sources, from physical to emotional, and not only is it essential for your overall physique and body composition goals to manage it, but also incredibly important for our overall health.

Today, we’re going to dive a little deeper into one aspect of this: how stress affects appetite. I see this coming up alot within the industry in conversations related to nutritional planning and conversations around dietary decision-making, and there’s some conflicting information out there.  

What Stress Can do to Your Appetite

I’m sure you’ve gone through a stressful period in your life; maybe you had a deadline coming up at work that necessitates 60-80 work weeks, and on top of that it put stress on your relationship as well. Maybe this is you right now.  I want you to think back to how your appetite was affected during that period. Maybe stress caused you to overeat or crave certain hyper-palatable foods, or on the other side of the spectrum, it’s possible you’ve totally lost your hunger and were maybe even undereating relative to your nutrition goals.

Here’s the key: there’s also a bridge to both ends of that spectrum that you might not have connected before.

We’ll be talking about all of that and more in this article (as well as in the related podcast episode), as we dissect the effects that stress has on appetite.

The Bridge Between the Two Worlds 

Again, I want you to think about how periods of high stress have possibly affected your own appetite in the past. There’s a big chance it could have been both of the aspects I talked about above; under-eating with subsequent over-eating. This is a bridge between the two opposite ends of the spectrum that most people experience under stress.

The primary study we’ll be discussing today shows that both instances generally happen. Suppression of appetite leads to fewer meals consumed, as well as an aversion to healthy foods, but also significant overconsumption of hyper-palatable ultra-processed food later on. This eating pattern in itself is a good proxy for a stressed or high cortisol client. 

Basically, the picture we’re painting is that stress generally makes you eat fewer meals overall because of reduced appetite, but then its followed by a major drive to overeat or binge on hyper-palatable food later on. This results in an overconsumption of calories overall with mostly nutrient-devoid foods, which describes so much of the over-stressed western population. 

We do have a particular study on this — it is an animal study, so please keep that in mind, as it’s essential to understand the difference between animal and human studies. Having human studies that are RCTs or systematic reviews is the most substantial level of evidence. We can still gain tons of good information from animal studies, however, and what’s important about this particular animal study is that the HPA access is conserved and nearly identical in humans. That means that we can carry over some of the principles, even if it is not necessarily done directly on humans. 

Sometimes we have to do research in this capacity because it might not be ethical to study specific variables on humans; for example, we can’t exactly crack a living human’s skull open and do brain biopsies to analyze things. Therefore, various rodent studies or animal studies are used in order to assess this. 

What was Uncovered in the Study?

In this particular research, we essentially had mice divided into groups — one receiving a restraint stress protocol, which is a very reliable way to induce stress and cortisol elevations, and the other group was the control group, so they did not receive any stressors. 

The mice then had various conditions of hyper-palatable food, which included lard and sugar-rich chow versus just regular mouse food alone. 

Let’s look first at the group of mice receiving lard and sugar-enriched food that was subject to stress. As we discussed a little bit earlier, these mice ended up eating less frequently, but then significantly over-ate these “comfort foods”, leading to increased adiposity and fat gain.

A very interesting to look at is the group of mice that had restraint stress, but only had access to standard food which wasn’t hyper-palatable. These mice ate significantly less than all the other groups, and they had the least amount of body fat by the end of the study, presumably because hyper-palatable food wasn’t available to binge on. 

The overall signal we’re seeing here is that if hyper-palatable food is absent or not an option, we see a decreased appetite for regular healthy food and typically body weight loss as a result. I’d be willing to bet right now that you’ve also seen this for either yourself or your clients throughout your lifetime. 

What Does This Mean for Humans?

Bringing this over to humans: We rarely, if ever, are in a situation where hyper-palatable processed food is out of reach, especially in today’s day and age with Postmates, OrderUp, and UberEats. We are even able to order groceries on demand depending on where you live, or simply get in a car and drive, or even walk to a local bodega or restaurant. We also have the worst case scenario, which is most of America: Folks keep these things stocked in their house.

Since most of your client’s pantries and fridges are stocked with some of this stuff and what’s not stocked is just a few finger taps away, this is another argument to actually work with clients, manage stress, and deal with stress in healthy ways, as opposed to just kind of resorting to some of these scenarios. A pantry re-engineer is always the best option, but for those living with other people, this option isn’t always available. 

This may not necessarily be something you see with a more intermediate-advanced client. Still, if someone’s starting on their transformation journey, this might be more of a habit for them or potentially an unfavorable tendency that we’re trying to get out of.

HPA Blunting from Comfort Foods

We were just talking about healthily managing stress, so what I’m about to go into is quite an interesting finding and highlights that there are ways to manage stress that result in worse health, or ways that result in better health.  

What the researchers actually found in this study is that consuming the comfort food actually blunted the cortisol response and HPA axis

Translated, this basically means cortisol was lowered from eating the sugar-lard food.  In other words, the mice legitimately “managed their stress” by eating junk. 

This effect was not seen by eating regular chow. Again, by eating hyper-palatable food, they were biologically managing stress by reducing corticotropin-releasing hormone or CRH. CRH is the first molecule in the cascade that eventually ends up in cortisol release, so you can think of it as halting stress at the source.

This is obviously the least desirable way to do this and results in fat gain and poor health. We don’t wanna manage CRH by eating hyper-palatable, super calorically dense food. This is only a temporary solution and it’s a very slippery slope to obesity, insulin resistance, and metabolic issues. 

We can draw parallels here to things like retail therapy, gambling, or substance abuse; while these may bring good feelings in the moment, they end up hurting us in the end. There are healthy ways to manage stress and unhealthy ways to manage stress. 

We’ll talk about stress management methods towards the end, but first, we have some more interesting effects of stress to dive into.

Caloric Efficiency in Stress 

Something else surfaced in this study that’s a little less intuitive; the stressed mice had significantly increased caloric efficiency. 

This means that their bodies were much more stingy with storing the calories instead of burning them more indiscriminately, so they were a little bit thriftier. This was observed by looking at the amount of weight gained versus the number of calories consumed.

Basically, the mice under restraint stress and eating the hyper-palatable food gained more fat than expected for the calories that they were eating. This finding also probably transfers to humans. 

We know that chronic stress in humans, amongst other things, causes changes in the microbiome that cause it to potentially harvest more energy from the food we eat, meaning more calories per gram of food. This is one plausible mechanism by which it could occur. 

Systemic Effects of Stress on Hormones – Appetite, Thyroid, and Beyond

Stress is obviously going to impact our thyroid, adrenals, exacerbate or potentially induce gut issues, and impact the brain in terms of shrinking the hippocampus (executive cognition) and hypertrophying the amygdala (fear and excitement – i.e. more reactive to stress). This is really a systemic effect of stress and why it’s so important to discuss stress management with your clients frequently.

The next thing to look at would be appetite-related hormones under stress. In this particular study, levels of leptin and insulin were also measured. One of leptin’s main functions is as a long-term satiety hormone, and insulin, besides regulating blood sugar, also acts as a short-term satiety hormone in animals and people who aren’t insulin resistant. 

The first finding was elevated insulin, which isn’t exactly counterintuitive or unpredictable. They ate more calories and therefore gained body fat, ate more sugar, and were stressed. All three of which can induce insulin resistance by themselves, but the combination makes it happen that much faster. 

However, leptin levels were highly increased in these animals as well. Usually this will decrease food intake in an attempt to mitigate further weight gain, but this did not stop these animals in this instance, so we can surmise that restraint stress quickly induced some degree of leptin resistance as well via HPA axis activation.. A good rule of thumb is that if we see high levels of a hormone but symptoms of deficiency at the same time, then there’s probably a resistance to that hormone occuring. 

When you combine both insulin resistance and leptin resistance, you get dysregulated appetite with higher cravings and energy crashes, even if chronic stress isn’t part of the equation. 

As I alluded to earlier, both of these hormones usually suppress appetite when they’re higher in healthy folks, but in states of leptin and insulin resistance, they lose this particular function. When you add the effects of chronic stress, which potentially can exacerbate those resistances and then itself causes seeking of hyper-palatable foods, you get the result of someone who’s single-mindedly gunning for the salty-crispy-fatties.

Ghrelin, the primary hormone that stimulates appetite, wasn’t measured in this particular study, but we’ve known for a while that chronic stress increases ghrelin concentrations across the board. This results in both higher baseline fasting ghrelin, but also ghrelin that doesn’t fall as much in response to eating. In other words, you’re hungrier when you’re not eating, and you also don’t get as much of a satiety response when you do eat. 

Hyper-palatable food consumption is probably biology’s most straightforward and fastest way to manage stress and bring down cortisol, but again, this leads to a pretty nasty combination of factors leading to poor cardiometabolic health and fat gain. 

Tying it All Together

As we tie it all together, chronic stress is going to facilitate fat gain in poor health in several ways and the appetite effects are just one part of that. This should be differentiated from acute stress that goes away, such as exercise or a form of hormesis. Acute stress almost always lowers appetite, whereas chronic stress may have this effect of temporarily under eating and then consuming hyper-palatable food later on, an anecdote I’ve seen over and over with clients. 

There might be some situations where training is going to lead to a little bit more appetite later on in the day; there are certainly people who will out-exercise their caloric threshold that they’re trying to adhere to, and we see that, for them, exercise is such a potent stimulator of appetite that they need to manage that. This doesn’t necessarily happen to everyone out there. 

As I’ve mentioned, playing this out with clients, there are people who don’t eat most of the day, but then tend to overeat at dinner and go really hard in the paint on those evening snacks while watching TV. They may not necessarily describe it to you like that in their check-in, but that’s a general sentiment. Maybe they’re fasting a little bit or going low calorie, making healthier choices while they’re training and maybe they don’t have a ton of appetite right after that, but then they’re potentially overeating a little bit later on. 

Managing Clients Stress

If your client is high-stress, it’s imperative that you manage it. There’s many ways to do this – But the gist of what we’re trying to accomplish is getting out of rumination mode; the place where we’re stressed about deadlines and whats to come or maybe that stupid thing we said to our boss 3 weeks ago. 

We do have a podcast on this: Episode 224. This is a deep dive on all the potential stress management practices and their effects. Everything from breathwork, meditation, and walks in nature, to creative therapies like art, music, etc. All those have a good effect on bringing stress levels down if you’re confused or unclear on exactly how to manage your own stress or your client’s stress. 

The biggest take home is that stress does impact appetite in a number of different ways for clients. Even if there’s potentially an acute period of undereating, they may overconsume later on and if it’s hyper-palatable food choices, then that can be detrimental to their transformation. 

Chronic stress is going to have a different impact than acute stress, both on HPA axis function and on appetite and food choice. So be sure to differentiate between the two; don’t be afraid of a little healthy acute stress, like exercise. This could also be the difference of just having a stressful day once in a while versus having a long-term stressor or something that’s going on repeatedly in the client’s life. 

Animal studies aren’t perfect, but in this case there’s going to be significant, if not total carryover with the details that could pertain to humans. We do always want to provide the context of whether we’re looking at animal vs. human studies, because normally there will be significant differences – But at the very least, they can give us some patterns and trends to look out for within human physiology.

Recap and Summary

As you’re thinking about ways to apply this to your clients, it is important to remember to communicate with your clients firsthand and understand what they’re going through. Understand the food choices they are making when they’re under stress, their particular appetite, biofeedback, the food that’s available to them.

Some of these particular values can be tested in serum labs, and to make the best choices for our client, we have to understand the connection between serum labs, biofeedback, their nutritional choices, and food journaling. All of these things go hand in hand to take a comprehensive 360 view of the client’s case, which is what we’re always trying to do with the FNMS Program and Metabolism School.

We can think of real-life scenarios and situations where the science of this particular research might apply. It may not be perfect, but it can teach us some things so that we can think about broader patterns and trends. 

Hopefully, this study brought some attention to this particular topic around appetite and stress, and how a clients’ behavior and food choices may change over time. 

Some additional human research to pay attention to in this particular case is this study. It examined how individuals levels of cortisol, ghrelin, stress, and other factors predicted their weight changes over the following 6 months. That was a super helpful resource for kind of tying some of this stuff together.

The bottom line here is that stress is going to affect your clients appetite in some way, shape, or form – And in the vast majority of cases, drive eventual over-eating (on top of its independent effects on other hormonal systems). If managing stress isn’t one of the main pillars of your coaching business, it should be now. 

References

Norman Pecoraro, Faith Reyes, Francisca Gomez, Aditi Bhargava, Mary F. Dallman, Chronic Stress Promotes Palatable Feeding, which Reduces Signs of Stress: Feedforward and Feedback Effects of Chronic Stress, Endocrinology, Volume 145, Issue 8, 1 August 2004, Pages 3754–3762, https://doi.org/10.1210/en.2004-0305

Chao AM, Jastreboff AM, White MA, Grilo CM, Sinha R. Stress, cortisol, and other appetite-related hormones: Prospective prediction of 6-month changes in food cravings and weight. Obesity (Silver Spring). 2017 Apr;25(4):713-720. doi: 10.1002/oby.21790. PMID: 28349668; PMCID: PMC5373497.

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