Study: The Link between Body Temperature and Physical Activity

Happy three generations males relaxing on hiking tourI used to offer extended commentary on new research in a weekly series called “Monday Musings.” I’d cover and summarize a study or two or three, give some commentary, and open it up for questions from the readers. It was a fun and informative way to spend a Monday. Well, with more and more research being published than ever before, and more and more people being interested in health than ever before, I figured I’d resurrect the practice and begin analyzing new research in brief, digestible chunks.

First study is “Historical body temperature records as a population-level ‘thermometer’ of physical activity in the United States.”1

I’m not a cold weather guy anymore. Years of living in Malibu and now Miami Beach have softened me. I’ll admit that readily. But back when I was a kid in Maine, I used to brave those cold blustery (even snowy) days without much in the way of cold weather clothing. My friends and I would stay out all day long and never stop moving, never really feeling the cold. We weren’t out there shirtless or anything, but we also weren’t wearing four layers. We weren’t bundled up.

And even now, when I go snowboarding, I can’t bundle up too heavily. If I’m really staying in motion, I’ll be in short sleeves or else I get too hot. The key is moving. All you have to do is move and the cold just bounces right off you.

That’s the basis of this new study, which uses body temperature data to gauge the level of physical activity in the United States over the last hundred years or so. The authors propose that higher body temperatures mean greater physical activity. And that’s a fairly sound conclusion, but I don’t think it’s the entire story. There are other factors that can lower body temperature.

The one that leaps out at me is our linoleic acid intake from seed oils. Over the past 50 years or so, we have eaten more seed oils than ever before and the linoleic acid content of human body fat has increased by 136%.2

Why does this matter?

Hibernating animals tend to massively increase their linoleic acid intake in order to deposit tons of it in their body fat in the weeks leading up to hibernation. This induces torpor, a state of low body temperature, body fat gain, and extremely low physical activity—so low that they don’t move at all.3 Does that sound familiar? Brad Marshall, the “croissant diet guy,” has been focusing on how linoleic acid intake regulates torpor and thus body temperature and metabolic rate for the past couple years. It happens to all mammals, not just squirrels, bears, and mice. Humans are not exempt from the metabolism-depressing effects of excessive linoleic acid intake.

The second study is called “The effect of vitamin D and magnesium supplementation on the mental health status of attention-deficit hyperactive children: a randomized controlled trial.”4

These were Iranian kids aged 6-12 with diagnosed ADHD who also had magnesium and vitamin D deficiency. One group got 50k IUs of vitamin D each week and 6 mg of magnesium/kg of body weight every day at lunch; the other group got placebo capsules and tablets. So if you were an 80 pound (roughly 36 kg) kid, you’d get 216 mg of magnesium. Sadly they didn’t mention what form of magnesium, but whatever it was, it managed to increase serum magnesium levels.

What was the result?

Kids who received vitamin D and magnesium had fewer emotional problems, behavioral issues, peer problems, and “total difficulties” than the control group received no supplements. This is a simple intervention with very little downside—in fact, the supplementation group had no side effects whatsoever, not even the upset stomach that can result from lower-quality magnesium supplements—and lots of upside. There’s a good chance that most kids have at least subclinical magnesium deficiency, and we already know that magnesium deficiency is linked to many serious conditions children suffer from, like type 1 diabetes and leukemia.56 Magnesium supplementation is a low-cost, essentially “free” intervention to try on just about every child out there.

What about magnesium from food? Sure, that’s great. Almonds, most legumes, pumpkin seeds, winter squash, fermented dairy are all pretty good sources of magnesium, but supplementation may be warranted because food magnesium levels have been dropping from historical levels. In other words, the amount of dietary magnesium our physiologies are used to getting on a historical and evolutionary basis are no longer present in most modern foods.

If you can’t get your kids to take magnesium pills, you can just work it into their diets.

Blackstrap molasses in milk.

Magnesium chloride powder sprinkled in their drinking water.

Magnesium-rich mineral water like Gerolsteiner.

Anyway, that’s what I’ve got for today. What do you think about these studies? I’m curious to hear your reactions. Until next time.

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 more than three decades 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 flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.

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