How Many Calories Does Stress Have?
I'll admit, this is a silly question. You can't eat stress! But this question makes a critical point about metabolism that the entire health and fitness world seems to miss: calories don't control metabolism, hormones do. And when it comes to hormones, the stress hormone cortisol is critical.
Not only can stress hormones impact how many calories you eat in a day, they can also impact the quality of calories you choose to eat and even influence how, and where, those calories might get stored or burned from. But if all that is true, how does the whole thing actually work? And what can you do about it?
The best way to think about hormones is as cellular messengers. They deliver information about what's happening outside the body to cells inside the body. A good way to think about cortisol is as the 911 hormone. It sends a message similar to first responders like firefighters and police officers. Cortisol plays both a protective role and adaptation role. It works against inflammation and also releases the body's sugar and fat stores to meet the demands of stress. Anything that poses a potential threat to the body will result in cortisol being called in to help.
I also call cortisol the Jekyll & Hyde Hormone. If you recall from the story, Dr. Jekyll was a kind, upstanding citizen but was bothered at times with dark thoughts. This worried him so he developed a serum to disconnect himself from his dark impulses. This worked only partly, splitting his psyche in two and creating his alter ego, the evil Mr. Hyde. The story is about the struggle between the good balanced side, Dr. Jekyll, and the bad extreme side, Mr. Hyde.
That's also a great way to think about cortisol. Many people see cortisol as an "evil" hormone that stores fat and shrinks muscle. Fact is, it's required for optimal health and actually burns fat, under the right circumstances. There's no question it can become destructive in certain situations, like when it's chronically elevated or continuously suppressed. When cortisol is too high or too low, it turns into the evil Mr. Hyde. When it's balanced, cortisol is more like the helpful Dr. Jekyll.
Hormones are like people – they behave differently depending on the environment they find themselves in and the people they're surrounded by. For example, high cortisol in a low-calorie state will produce a different outcome compared to high cortisol in a high-calorie state. Same thing with exercise – you WANT cortisol high while you're exercising; you want it low when you're not.
During exercise, cortisol works with your other fat burning hormones, the catecholamines (adrenaline and noradrenaline) and growth hormone, to increase fat release. High cortisol levels when you're not exercising? That's a different story. When cortisol is "socializing" with insulin instead, it has the exact opposite effect.
Cortisol & Insulin
Understanding these hormonal interactions is important. Technically speaking, cortisol is both a fat storing and fat burning hormone. This is because it increases the activity of lipoprotein lipase (LPL), the body's major fat storing enzyme. But it also increases the activity of hormone sensitive lipase (HSL), the body's chief fat releasing enzyme.
Growth hormone and catecholamines, which are higher during exercise and fasting periods, accentuate cortisol's fat burning potential while suppressing its fat storing potential. In the fed state, when insulin is around in high amounts, HSL activity is turned way down while LPL activity is cranked up. In this way, insulin magnifies cortisol's fat storing properties while blocking its fat burning activity.
Cortisol and insulin also block the action of each other by decreasing the sensitivity of their respective receptors. This means that eating is not the only way to become insulin resistant; stress can do it too. So, cortisol is actually NOT a fat-storing belly-fat hormone like you've been told. Insulin and cortisol together, with a high-calorie diet, are the real cause of belly fat.
Cortisol & Thyroid
Another dual action of cortisol is how it interacts with the body's main metabolic fat burning engine, the thyroid gland. Cortisol and the catecholamines sensitize thyroid receptors. So low cortisol can also lead to low thyroid activity. High cortisol blocks the normal conversion of inactive thyroid (T4) into active thyroid (T3). So, like Goldilocks, you don't want cortisol too low or too high, but just right.
Cortisol & Hunger
There are two things required for fat loss – a calorie deficit and hormonal balance. Cortisol impacts hormonal balance, but it also impacts calories. Cortisol impacts several hormones responsible for hunger and cravings. These include leptin, insulin, and neuropeptide Y (NPY).
The command and control center of your metabolism is an area of the brain called the hypothalamus. This is the center of your metabolic sensor/thermostat. This area needs to "hear" the signals being sent by peripheral hormones like leptin and insulin, both of which shut down hunger in normal circumstances. Chronically elevated cortisol levels cause irritation in the hypothalamus leading to downregulation of hormone receptors inducing hormone resistance.
Imagine walking into a room with a strong odor and covering your nose and mouth, only to realize later you can no longer smell the odor. This is what cortisol does to the brain. It muffles its satiety sensing mechanism. This makes it far less likely you will feel satisfied from meals and far more likely you'll eat more at current and future meals.
Cortisol & Cravings
Cortisol is also involved in cravings. By mechanisms not fully understood, cortisol along with other stress hormones (i.e. the catecholamines), increases desire for more palatable, calorie dense foods. It does this while simultaneously shutting off the goal oriented centers of the brain and ramping up the reward centers of the brain. This is a bad combo if you want to stick to your diet. In other words, there's a reason we want a triple decker boo-boo burger when we're stressed rather than the chicken and broccoli already prepared in the refrigerator. Cortisol may be part of that reason.
If you're a savvy fitness enthusiast, when you think stress you think cortisol. If you're really on your game, you'll also think catecholamines. But there's one more hormone produced by stress that even the most advanced experts know little about – NPY.
NPY is involved with hunger in the brain as referenced above. But cortisol doesn't just impact brain NPY, it also impacts body NPY. When you're under acute stress you release catecholamines and cortisol. When you're under chronic stress you release more NPY. When catecholamines and cortisol are "socializing", they help you burn fat. But NPY makes you gain fat, especially when it's hanging around with cortisol.
When NPY is released in large amounts it causes immature fat cells to grow into mature fat cells. Chronically high cortisol makes the body more responsive to this fat storing action of NPY. In other words, NPY increases fat cell growth and cortisol makes it more efficient at doing it. If you're confused, here's what I just said:
- Cortisol combined with catecholamines, like it is in short-term stress, helps us burn fat.
- Cortisol combined with NPY, as it is in chronic stress, equals increased fat storage.
Cortisol is made in the adrenal glands mostly, but there's one other place it can be made – belly fat. The deep fat of the belly, called visceral belly fat, contains an enzyme called 11-beta hydroxysteroid dehydrogenase (11-HSD). This is an enzyme that converts inactive cortisone into active cortisol. This means belly fat can produce its own cortisol!
And in another twist in the complicated relationship between insulin and cortisol, insulin increases 11-HSD activity, which increases cortisol levels which then causes increased insulin resistance. In this way, belly fat acts like a parasite ensuring its growth at the detriment of the host. I bring this up because there are many situations where stubborn belly fat remains despite best efforts with diet and exercise. Sometimes an extra hour in bed, to lower cortisol, may be a better strategy than an extra hour on the treadmill.
There's a lot more to the story of cortisol, but let's examine some things you can do to manage cortisol. The three best ways to control cortisol are diet, exercise, and lifestyle. And the three easiest ways to assess if cortisol is balanced is by paying attention to hunger, energy, and cravings (HEC or "heck"). If your HEC is in check, it's a rough indication that cortisol is as well.
Remember, cortisol is an alarm hormone. It may surprise you to know that both eating and not eating can raise cortisol levels. Skipping meals can raise cortisol because the brain requires a constant supply of glucose. For some, skipping meals will cause blood sugar changes that create a cortisol response. For these types, doing this too much can start causing many of the negative effects mentioned above. Eating can raise cortisol too. Again, cortisol is the alarm hormone and helps regulate the immune response. In those who have food sensitivities, this effect can be pronounced.
When it comes to eating frequency, don't get caught up in what the research zombies are telling you. Let research refine your approach, not define it. There are many approaches that can work. Eat frequently enough to keep your HEC in check. For some this may mean lots of small frequent meals. For others it may mean fewer smaller meals.
There is no one-size-fits-all here. Just remember that a healthy low calorie meal is neither healthy nor low calorie if you find yourself crushing half a cheesecake at the end of the day. And while there's a lot of controversy recently over meal timing, one possible benefit to a post-workout recovery drink is the quick suppression of post-workout cortisol.
Cortisol and Exercise
Short intense exercise, or exercise that's weight training dominant, and slow relaxing exercise are best for cortisol. In the case of short intense exercise, cortisol is elevated along with growth hormone and the catecholamines. That's good for fat burning. Plus the shorter duration may mean less compensatory hunger later and less chance of going catabolic.
With longer-duration moderate and intense exercise, cortisol can easily dominate over the growth promoting hormones and be associated with more post-workout hunger and cravings and less anabolic potential. Is this the reason sprinters and marathoners look so different? Probably not entirely, but after accounting for genetics, it's not a huge jump to suggest this mechanism is playing a role.
Another great way to lower cortisol is finishing workouts with slow relaxing movements like leisure walking. I'm not sure why this isn't used more often, but slow walking is one of the best approaches to lowering cortisol. And it has been shown to be even more impactful when done in a nature setting.
Finally, if you really want to beat cortisol you should develop a new appreciation for what I call rest-based living. Find as many opportunities as possible to prioritize R&R workouts. These include naps, sex/physical affection, massage, foam rolling, laughter, time with pets, leisure walking, sauna, hot baths, contrast showers, meditation, etc. All of these activities have application in lowering cortisol.
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