My typical approach to most things medical is “oh, that’ll go away” or “I don’t have to worry about that yet.” I’m not irresponsible by any means – I know when to go see a doctor, and I do. But if I have a sore hip or elbow or if my lower back aches, I’m pretty confident that’ll it go away eventually. If it gets to the point where it’s months, then I know I should probably go in for a look.

Things like metabolism, on the other hand, seems like stuff that floats around in the vast distance. In my 20s and 30s, I recall an older friend often saying “just wait until you hit your 40s and your metalbolism slows down.” Well, I didn’t really know what that meant and I didn’t pursue the knowledge. Why? Well, go back and read the first sentence of this post. I think I’ve always just thought of metabolism as tied to the energy my body produces as a result of my food intake or something. And that when my metabolism slowed down, I’d have to change my eating habits or exercise even more so that I didn’t gain unhealthy weight.

This week as I was reading my various news feeds I came across this article from the Scientific American about metabolism and I thought to myself that it was time to dig in and learn more about this thing that was supposedly going to show up one day, slap me upon the face and render me a useless sloth.

I know, I know, I had decades to just pop it into Google, so why now? I don’t know. I don’t have to explain myself! The urge just hit me. Lo and behold, the article is more interesting and fun than you might think when you hear the words “metabolism” and “Scientific American.” Witness here, the author talking about his daughter’s seventh birthday party:

Aside from the fresh veggies left wilting in the sun, none of the food was recognizable as a product of nature. The cake was a heat-treated amalgam of pulverized grass seed, chicken eggs, cow milk and extracted beet sugar. The raw materials for the snacks and drinks would take a forensic chemist years to reconstruct. It was a calorie bonanza that animals foraging in the wild could only dream about, and we were giving it away to people who didn’t even share our genes. All this to celebrate some obscure astronomical alignment, the moment our planet swept through the same position relative to its star as on the day my daughter was born. 

Scientific American, January 2023

Not exactly what went through my mind during my kids birthday parties, but I digress. The author is an “evolutionary anthropologist” and the article goes on to report out on a study done by he and his colleagues, where they made “important strides in understanding how our bodies use energy” and how their findings “have overturned much of the received wisdom about the ways human energy requirements change over the course of a lifetime.”

So my very amatuer understanding of metabolism seems to be in the ballpark. The author further defines it for me in the article:

Our metabolism is the energy we expend (or the calories we burn) each day. That energy comes from the food we eat, and so our metabolism also sets our energy requirements. Calories in, calories out.

Herman Pontzer, Scientific american, january 2023

And there you have it. Bascially every phase of our life, every minute of it in fact, requires some kind of energy. Our growth, reproduction, day-to-day needs – all driven by food and energy. I won’t ruin the rest of the article for you – you really should read it – but it goes to talk about the results of the study and as it turns out, my older friend was both wrong and right about metabolism “coming for me” in my 40s and 50s. Wrong because I’ve managed to stay active and eat relatively healthy, therefore my energy has generally been good and consistent. But he was right because it really depends on your food intake, exercise regimen and yes, those pesky genetics. Turns out that metabolism stays remarkably consistent until about age 60, but of course depending on how you treat yourself in the run-up to that age.

Check out that blue area on the graph on the right – very consistent from age 20-60.