Here's why you exercise so much and still can't lose weight

Story highlights

  • People who exercise a lot may hit a plateau above which they do not burn more calories
  • Experts think we may have evolved to limit our calorie burn to keep from starving
  • You may be able to break the ceiling by changing up your exercise regimen

(CNN)If you are intensifying your running regimen in hopes of losing weight, you might be running around in circles: There is a limit to how many calories we can burn through exercise, a new study suggests.

The grim message comes from a small study of a group of 332 adults living in the United States, Jamaica and Africa, some of them more sedentary and some more active. A team of researchers measured their activity level for seven days using an accelerometer, similar to the kind in the Fitbit and other wearable devices, and also measured the number of calories the participants burned over the week.
The researchers found that the participants who moved more also burned more calories, but only up to a point. The most active people hit a plateau and did not burn any more calories than their less-active peers.
    Although the researchers did not look at the specific activities that participants were doing, the level on the accelerometer at which calorie burning peters out would be achieved "if you're walking a couple miles a day, like to work and back, taking the stairs instead of the elevator and trying to exercise a couple times a week," said Herman Pontzer, associate professor of anthropology at Hunter College, and lead author of the study, which was published on Thursday in the journal Current Biology.