Dear Mark: Cold Weather Carb Cravings, Muscle Loss in the Military, and Pain During Exercise

Cold WeatherFor today’s edition of Dear Mark, we’ve got a two-parter. First, I cover why our desire for carbohydrates might increase in cold weather (hint: it’s probably all the shivering our muscles do in an attempt to stave off the chill). Second, I discuss why a military man might be losing muscle mass when out in the field, despite (or, perhaps, because of) all the hard physical work he’s doing. Even if you’re not military, the answer will likely still be helpful. And after that, Carrie lends a bit of sage advice to a reader who ends up with debilitating pain in her thighs every time she does high intensity plyometrics. The answer may not be what she had hoped for, but it’s probably the right one.

Let’s go:

Hi Mark,

I am currently working a job where I spend every other week living outside leading backpacking trips. In the winter, temperatures will be in the 20s or 30s during the day and colder at night. I’ve noticed the last couple weeks that as the weather gets progressively colder, I’ve started craving carbs more and more. I was wondering if I need more carbs to help keep my body warm if I’m living for 8 days at a time in that cold of weather?



It could be a couple things.

The first thing I would guess is that you’re simply burning more fuel, particularly glycogen, acclimating to the colder temperatures. For example, shivering is used to generate heat and maintain body temperature in the face of cold exposure, and it utilizes a variety of fuel substrates, including lipids, glycogen, and to a much less extent, amino acids. But here’s the thing: even if you’re burning 50% lipids and 40% carbs, you have plenty of body fat to draw upon before turning to dietary sources – even the very lean have pounds and pounds of pure animal fat at their disposal. You’re not going to crave fat, necessarily, because you don’t need to eat any to replenish your stores.

What about glycogen? Glycogen stores are smaller, somewhere in the 400-500 gram range depending on the amount of lean mass you carry. Big muscular men will have larger glycogen stores (but they’ll also use more moving that mass through space). Women tend to have less lean mass and therefore smaller glycogen stores. Burning through glycogen increases the dietary desire for carbohydrate because dietary carbohydrate is the quickest way to replenish glycogen. You can generate it from protein (either through the diet or taken from your own lean mass) through gluconeogenesis, but the body prefers to get it directly. Fewer steps that way (plus, protein’s better used for other things). So, if you’re spending eight days outdoors where the temperature never gets much higher than freezing, you’ll be burning through a lot of glycogen – and craving carbs – simply from all the shivering you do. Throw in some activity (backpacking all day) on top of that and you’ve got a recipe for carb cravings.

You may also be experiencing a natural seasonal variation in hunger. Some researchers have even suggested that seasonal affective disorder, which as you know occurs during winter when the days are short and sun is scarce, might be an evolutionary adaptation that favors energy storage in otherwise inhospitable conditions. I can see that. SAD makes you sad and kind of gloomy, so you’re less likely to put yourself out there and take risks. It reduces your desire to exercise, which conserves energy. It lowers libido. It’s even associated with carb cravings. Nowadays, in our energy replete, already sedentary, carb inundated society, SAD has an overall negative impact on health. It’s not fun (or helpful) to be depressed, crave junk food, feel lazy, or have no libido. But thousands of years ago, it might have improved survival by keeping people alive, conserving energy, increasing energy stores, and limiting procreation in an energy-poor environment (which can have negative epigenetic effects on the fetus).

Under your circumstances, I think additional carbs may be warranted. Eat to your appetite.

My husband is in the military; when he goes to the field (any amount of time), he doesn’t eat a lot and does a lot of physical work. He comes back with way less muscle, and maybe a little fat loss but virtually the same. Why? Shouldn’t his muscles be using the fat instead? Can you clear this up? Thanks 🙂


This is a textbook example of tons of physical activity coupled with low calorie intake begetting chronic elevations in cortisol. Let’s unpack this a bit.

Your husband is highly active in a demanding environment without eating enough food. If he’s wearing kit, that can add fifty, sixty pounds to the equation. He’s essentially on a chronic low-calorie diet, which is known to increase cortisol levels. Now, cortisol isn’t all bad. That burst of cortisol we secrete first thing in the morning can actually help mobilize fat stores. The problem is when cortisol is chronically elevated, as with formal dieting or doing lots of physical work without eating much. That’s when abdominal and visceral fat can accumulate and muscle begins to atrophy. The relationship between chronic cortisol and skeletal muscle is well-established. Older folks with the highest cortisol levels tend to have weaker grips than folks with normal cortisol, and those with high cortisol-to-testosterone ratios have reduced muscle strength.

I’m fairly certain this is the culprit.

It comes down, as it always does, to the question of acute versus chronic stress. A modest calorie deficit and exercise several times a week with generous refeeds is a good way to lose body fat. Your body won’t “think” you’re starving. It won’t buckle down and start making tough choices regarding which tissues to break down for fuel. Maintaining a severe calorie deficit and excessive exercise regimen for extended periods of time signals famine. Muscle is metabolically demanding. It’s awesome and useful and physically attractive, but it requires a lot of nutrients to maintain. If nutrients aren’t coming in for the foreseeable future – if your body thinks you’re experiencing famine – muscle will wane.

Muscle can’t be built (or even maintained) without the necessary building blocks: calories, fat (for hormone production), and protein. Your husband isn’t getting enough, and he’s burning through what little he does eat. Since the physical activity is probably nonnegotiable, his best bet is to cram as much food down his gullet as possible. This may mean eating less-than-Primal fare. Given the situation, that’s okay.

Good luck!

Dear Carrie: Pain During Exercise

My thighs (quads) kill me when I perform certain exercises such as squatting down, jumping up explosively, landing, and immediately repeating. Or when I do burpees, or do an exercise where I place my palms on the floor, invert myself into an upside-down V shape, and hop my legs from side to side, lifting my lower body with the core. Tuck jumps hurt. Even if I bend down to touch the floor, jump high up, and then land and bend down again on the other side and repeat… all of these exercises very quickly build pain in my quads that is excruciating to me and forces me to stop. When I do, the pain fades away within a minute.

Is this an overload of my muscles or what? I can’t seem to fully understand whether this is natural, if I did anything to cause it, if it will ever go away (I am praying it will). The seemingly constant and lurking presence of this possibility when I engage in such plyometrics (which I really really want to do) weighs down on my self-confidence and faith in my body.

I’d love for your feedback and advice with this nagging problem. =)

Thank you so much!


You have to slow down. Way, way down. It sounds like you may be trying to do too much too fast (literally; your exercise choices are intense and high speed). The excruciating pain is a warning sign that you’re risking serious damage to your body. That the pain disappears almost immediately is a “thank you” message meant to convince you to slow down the exercise. It’s best to listen to your body when it’s giving you such clear signals, or you risk doing some long term damage.

I’ve been there as well. I understand the urge to push through the pain at almost any cost. For years I had to get in a hard workout every day (usually some form of chronic cardio) or else I’d feel like the day wasn’t complete. Mark, as you probably know, used to be like this too, and maybe that’s part of the reason we got along so well: we bonded over our mutual addiction to exercise. The only way I got over it was to just stop doing the things that took a real toll on my body. I stopped running. I stopped going to the gym every day. I started hiking a lot and making my intense workouts much shorter (and by extension more intense and less frequent) than before. And it was hard and I worried I was going to gain weight and lose my fitness level. I stuck with it, and when those things didn’t come to pass and my fitness and body improved if anything, I was over it for good (at least so far!).

When I look at the exercises you describe, I see a lot of redundancy. Jumping squats, burpees, upside down hopping Vs, tuck jumps, and that other exercise that involves bending over and jumping – they’re all very quad dominant and they all involve a ton of force applied to very specific tissues. Namely, your thighs. There’s some core and some other stuff being worked, but it’s a lot of jumping and landing. That will add up over time and it seems like it is adding up already. When you get back into intense movements, stick to one per workout. Don’t ramp up and throw all those exercises at your body in one workout. You’re probably still growing, and even if you aren’t and you are a full grown adult, that would still be a heavy load for your legs.

Honestly, it comes down to the pain. If the pain is there, you’re doing something wrong and you need to rest.

So here’s what I would suggest:

  • Stop the calisthenics for the foreseeable future.
  • Use a foam roller before you train to help massage and release tight muscles. I use Trigger Point Performance Rollers by
  • Try a weekly yoga class for increased flexibility, increased muscle strength and tone and protection from injury. (I may do 2-4 classes a week.)
  • So you don’t go crazy from inactivity, walk or hike a couple miles a day. Maybe even a couple more.
  • After a weeklong rest, start some easy, slow strength training. Bodyweight movements are fine. Dumbbells or barbells too. Stick to compound, full-body movements. Twice a week to start.
  • If you ever do go back to calisthenics, try box jumps. You still get the advantage of jumping as high as you can but you land on a box at the peak of your jump. This reduces the impact to your legs and joints. It’s easy to overdo box jumps, though, so be careful. Think quality and form over quantity. Note that it takes about 120 hours for your body to fully recover from box jumps (probably even longer for other, more stressful forms of calisthenics).
  • Sprints once a week. I find sprints have been by far the most effective in toning my butt and thighs, sometimes I’ll do them twice a week. Sprint uphill to reduce the impact.
  • Play! Find something you love doing, like a sport or any other physical activity that doesn’t involve repeating the same motion over and over again. (I love taking long beach walks and hikes with Mark!)
  • If the pain persists, see a medical professional and/or physical therapist.

Good luck and be sure to write in if you need anything else!

Well, that’s it for this week, folks. Got any questions for me and Carrie? Ask away in the comment board, and we’ll try to answer them in future blog posts. Thanks for reading!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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