For every 100 calories we burn while exercising, we automatically gain at least 28 of them, hampering our best efforts to lose weight with physical activity, reveals a new study.
The results also show that carrying extra pounds unfortunately increases calorie compensation, making weight loss through exercise even more elusive for those who are already overweight.
The study also suggests that calorie compensation varies from person to person, and that learning how the metabolism responds to training may be the key to optimizing exercise to control weight.
In theory, exercise would substantially help with weight loss. When we move, our muscles contract, requiring more fuel than at rest, while other organs and biological systems alike expend extra energy. Thanks to previous laboratory studies, we know approximately how much energy these processes require.
Until recently, most people assumed that this process would be additive—that is, walking a single kilometer and burning 100 calories. Walk two, burn 200 and so on, in a logical and mathematical way. If we don’t replace those calories with extra food, we’ll end up burning more calories than we consumed that day and start losing pounds.
But this rational result rarely happens. In study after study, most people who start a new exercise program lose less weight than would be expected based on the number of calories they burn during workouts, even if they strictly control their diet.
Some scientists have begun to speculate that energy expenditure may be less elastic than we thought. In other words, it can have limits.
This possibility gained strength with the publication of this study was published in Current Biology.
Scientists have begun to see what happens to metabolism when we move. They collected data from 1,754 adults. UUsing statistical models, they were able to calculate whether calories burned during activity increased people’s daily energy expenditure as expected—that is, whether people burn proportionately more total daily calories when they move more.
found that not. In fact, most people seemed to be burning only 72% of the extra calories.
“People seem to make up for the extra calories burned by activity by at least a quarter,” said Lewis Halsey, a professor of life and health sciences at the University of Roehampton in London and one of the study’s lead authors.
Unexpectedly, researchers also found that energy compensation levels increased among people with relatively high levels of body fat. They tended to offset 50% or more of the calories they burned by being active.
Importantly, the study did not analyze people’s food intake. It focused only on energy expenditure and how our bodies seem to be able to offset some of the calories burned during exercise by reducing biological activity elsewhere in the body.
But the new science of exercise and calorie compensation isn’t entirely disheartening. Even people whose bodies make up 50 percent or more of the calories they burn during physical activity will burn more calories a day than if they sit still, Halsey noted. To lose weight, we will also have to eat less.