Exercise is not an effective way to lose weight (though it is awesome for you in plenty of other ways). In short, our bodies want to burn a certain amount of calories per day and it’s hard to change that. This is the central theme of Pontzer’s book, which I found interesting and thought provoking
Summary
Why doesn’t exercise work for weight loss?
In short, our weight is controlled by “CICO” – calories in v calories out. Calories in is food. Calories out comes from exercise, simply being alive (i.e., your kidneys and brain need to consumer calories to function), as well as other activity you do (e.g., fidgeting)
Our bodies want to conserve energy, so calories burned while exercising are often offset in other places (e.g., you will fidget less during the day, your body will spend less calories on maintaining itself, etc.). We are this way due to natural selection - for most of human history, access to food was unpredictable, so being able to store excess energy and be “efficient” helped people survive during famines
You’ll also be hungrier and eat more food if you exercise more
We know this from multiple sources:
If you track studies where people start exercising, weight loss looks good in the beginning, but slows down more than you’d expect over time as people’s bodies adapt and start burning less calories
He spends time with the Hadza – a super active tribe in Africa that spend their days hunting and foraging for food (chasing antelope, digging up tubers). Using modern techniques to measure caloric expenditure, he shows that they burn the same amount of calories as the average American
So what should we do?
First, exercise is still really good for you - mental health, physical health, etc. It also regulates appetite and helps people maintain weight loss
As a result, to lose and maintain a healthy weight, one should focus on moderating calories in. This is obviously really hard in our current food environment. He simply suggests that one:
Follow whatever diet works for you and allows you to eat less calories than you burn over a long period of time
Eating less calorie dense foods and avoiding hyperpalatable foods (or “this is I love it” foods as my toddler calls them)
The reason the Hazda don’t have obesity isn’t necessarily because of their activity levels - it’s because they don’t have processed, impossibly delicious food like we do. The food they eat, he reports, is probably not tasty enough to overeat on like a can of Pringles
Thoughts and reactions
I thought this was pretty interesting / though provoking, but also makes intuitive sense. Think about the last time you did a really tough workout or were really active in one day – you probably wanted to spend time on the couch after, right?
I thought the title overpromised relative to a pretty straightforward answer (“exercise is good, eat less.”) Probably not his fault, but at this point, how much “new science” is really left?
This book is a reminder that what you don’t do is sometimes more important than what you actually do. We often want to equate activity with motion and progress, but sometimes refraining from something is more important (and more productive). The best example I can think of is having a “filter” on what you say, whether in personal / professional relationships. Or if you are trying to save money, not spending is a lot easier than making more money overnight
The book’s suggestions (don’t eat too many calories, exercise) are good examples of “simple, not easy”