We have this idea that if we want to lose weight, we need join a gym on January 1st. Then, we start working out regularly, and eventually we’ll slim down. Well, here’s some bad news. We found more than sixty studies on this, and it turns out exercise is actually pretty useless when it comes to weight loss. Dr. Kevin Hall at the National Institutes of Health has done some of the most important studies on exercise and weight loss. The results suggest that there is a need to rebrand exercise… Exercise isn’t a weight loss tool per se. It is excellent for health and, other than the the cessation, it is probably the best single thing that one can do to improve their health.
But we should avoid thinking of it as a weight loss tool. While exercise will definitely help you live a longer, happier life…. It’s just not the best way to lose weight. And the reason has to do with how our bodies use energy. You may not realize it, but physical activity is actually a tiny aspect of our daily energy burn. There are three main ways our bodies burn energy. These include our resting burn rate, so that’s how much energy our bodies burn just for basic functioning or just to keep you alive, basically. The other part of energy expenditure is the thermic effect of food, and that’s just how much energy is required to break food down in our body. The third part of energy expenditure is kinesthetic. For most people, physical activity – that’s any movement we do, only accounts for about 10 to 30 percent of energy use. So the vast majority of energy or calories we burn every day comes from our resting metabolism, over which you have very little control. While 100% of your “calories in” are up to us, only up to about 30% of our “calories out” are in your control.
One study found that if a 200-pound man ran for an hour, 4 days a week for a month, he’d lose about 5 pounds at most, assuming everything else stays the same. But, of course, everything else doesn’t stay the same! Researchers have found we make all kinds of behavioral and physiological adaptations when we start increasing the level of exercise we’re getting daily. For one thing, exercise tends to lead to eating more. And I’m sure you know the feeling: you go for a spinning class in the morning, and then by the time you eat breakfast you’re so hungry you maybe double the size of the portion of cereal you normally eat. There’s also evidence to suggest that some people simply slow down after working out, so if you went running in the morning you might be less inclined to walk as much at work. These are referred to as: “compensatory behaviors” — the various ways we unknowingly reduce the effects of our workouts. Researchers have also observed a phenomenon called: “metabolic compensation”.
As people start to slim down, their resting metabolism can slow down also. Therefore, the amount of energy you burn while at rest is lower. That means this bar might shrink as you start to lose weight. There’s still a lot of research to be done, but one study from 2012 is very interesting. They went out into the middle of the Savannah in South Africa to measure the energy burn among an indigenous group. These are super-active, lean hunter-gatherers. They’re not spending their days behind a computer at a desk. And what they found was shocking. What we found is that there was no significant difference. Even though the study group has a much more physically active lifestyle, they weren’t burning any more calories every day than adults in the US and Europe. Somehow the energy they used for physical activity was being offset by other behaviors. So, how do they stay slim? …They don’t overeat! Based on this kind of information, we can see that the calories that we burn off in exercise, can be undone fairly quickly. It would take about an hour of jogging to burn off a Big Mac and fries.
You’d have to spend about an hour dancing pretty vigorously to burn off three glasses of wine you might drink with dinner. An hour of cycling really intensely on exercise bikes to burn off a couple of doughnuts. That’s why exercise is best seen as a healthy component of a strategy that is focused on food. But despite extremely high obesity rates in the US, governmental agencies as-well-as private companies with an interest in making sure we keep eating and drinking their products, continue to present exercise as a solution.
Since the 1920s, companies like Coca-Cola have been aligning themselves with the exercise message. The idea here is that you can drink all these extra bottles of soda as long as you work out. But as we’re seeing, it doesn’t work like that. Actually burning off those extra calories from a can of soda is really, really hard. We have an obesity problem in this country, and we shouldn’t treat low physical activity and eating too many calories as equally responsible for it.
Public health policymakers need to really prioritize improving our food environment (ie., public education and perhaps regulation) to help people make healthier choices about our food and drink. While It’s not impossible to lose weight through exercise, it is much more difficult. Plus, we need to recognize what dynamics are at work in the process. If you do go to the gym, and you burn all those calories, it takes you a long time to do so and you put in a great amount of effort. Recognize that you can erase all of that in five minutes by eating a slice of pizza. Relative magnitude is actually quite surprising, and most people don’t fully appreciate that.