But it's not necessarily true, a research team says. They found that people who exercise a lot don’t burn extra calories for their efforts beyond a certain point. Their new study is published in Current Biology.
Don’t drop that gym membership just yet, though. WebMD asked two experts to discuss these findings and the role of exercise.
The experts include the study’s lead researcher, Herman Pontzer, PhD, a professor of anthropology at City University of New York, and Edward L. Melanson, PhD, an associate professor in the division of endocrinology, metabolism, and diabetes at the University of Colorado Anschutz Medical Campus, Aurora.
On one point both agree: The new research is not discouraging exercise, which is crucial to keeping your body and mind healthy. But it does provide more evidence that diet, not exercise, is the key to losing weight.
What did the study find?
Pontzer and his team measured the daily activity levels of more than 300 men and women -- along with how many calories they burned -- over the course of a week. They came from five different countries across Africa and North America: the U.S., Ghana, Jamaica, the Seychelles, and South Africa. People in some of those nations tend to be more physically active than many Americans.
The researchers had everyone's body mass index (BMI). They measured activity and calorie burning for a week, but didn't track whether people gained or lost weight.
Exercise did have an effect on how many calories people used, called energy expenditure. But the amount of calories burned didn’t increase dramatically as people got more exercise. Those who had a moderate activity level burned a few more calories daily, on average around 200, compared with the most inactive people. But those who exercised beyond the moderate activity level saw no effect of their extra effort as far as how many calories they burned.