Why You Don't Have To Earn Food Through Exercise
In today's society we are bombarded with messages about how great and healthy exercise is. The more the better. No pain no gain. You better earn your calories. Etc etc. Since I haven't been living under a stone (given my background) I was of course influenced by this toxicity. I often had the feeling that I could eat as long as I was exercising. No movement meant less permission to eat. After I came across the work of Dr. Herman Pontzer it got a lot easier for me to deattach food from exercise. Dr. Pontzer is a evolutionary anthropologist who has conducted a lot of research on human metabolism. In a recent study of his, he spent time with Hadza, a traditional hunter-gatherer community in northern Tanzania. Its inhabitants are about 5 to 10 times more physical active every day compared to the typical American. He and his team wanted to measure the calories burned by Hadza, the hypothesis being that they would burn significant more calories than us sedentary developed, industrial populations. They used a really precise technique called "doubly labeled water" , the participants drank a special water labeled with isotopes of oxygen and hydrogen, urine tests told the scientists their calories burned per day.
When the results came back the scientists were totally shocked. Because even though the Hadza are much more physically active than the average European/American, it did not burn any more calories than adults in the US, Europe or other industrialized populations! They were so shocked by the result that they conducted a new study using a heart rate technique. But they got the same answers no matter how they measured it.
This suggests that daily energy expenditure is constrained according to Dr. Hadza. Your body adapts to exercise to keep energy expenditure within a narrow range. The human body seems to adjust to physical activity by saving calories on other physiological processes to keep total energy expenditure in check. All of these systems that we aren't even really aware of (including your reproductive health) are actually where you spend the bulk of your calories. If you are really active you'll be spending a bit (or much) less on those other processes to sort of make room for the physical activity. In other words, the calories that you are obsessed with burning for your body on exercise and movement, your body will save up on other places like keeping you warm, digestion, libido, reproductive health (as in period), immune system (people with HA often experience a low count of white blood cells), ... Talk about doing your body a disservice.
Our bodies aren’t simple calorie-burning engines that we can easily manipulate to keep us looking trim and feeling good. They are complex and dynamic metabolic systems meticulously shaped by evolution for survival and reproduction. For our bodies it makes sense to slow down metabolism as a response to overexercising, famine or starvation.