A recent study suggests that exercise is less effective at helping obese people lose weight than lean people. This is because the resting metabolism slows down more to compensate for the additional energy expenditure during exercise. For each additional calorie burned, half is saved again. In extreme cases, affected people gain weight rather than lose it because their overall turnover remains the same or even falls.

Ottawa (Canada). Almost every modern diet recommends consuming 500 to 600 kcal less than the required total turnover, directly or indirectly – this must be achieved through appropriate dietary changes and increased exercise. The latter increases energy consumption and thus also the resting metabolic rate, which the body needs to maintain vital functions – at least that is the current theory. All you have to do is use your body values Calculate the basal metabolic rate of calories,

But is this calculation even correct? That’s exactly what Vincent Kerro of the University of Ottawa asked himself. To do this, he and his colleagues evaluated data from 1,750 men and women whose total and resting energy requirements were determined using routine laboratory measurements of respiratory gases and isotopic labeled water.

Based on this data, the scientists wanted to find out to what extent the energy consumption caused by increased exercise actually alters the resting metabolic rate. So far, different theories have come to the fore regarding this. According to one hypothesis, the resting metabolic rate increases with increasing speed, for example because additional muscles consume more energy even at rest. Other models suggest that the resting metabolic rate either remains the same or decreases as a result.

Excess exercise lowers the basal metabolic rate of calories

The studies showed surprising results. Only a fraction of the extra calories burned during exercise actually affect overall metabolism. “On average, in a normal person, only 72 percent of the extra calories we expend through increased exercise manifest themselves in total energy expenditure that day,” Caro and colleagues wrote in the journal. current biology, The remaining 28 percent of caloric turnover is completely broken down and does not appear in the daily balance.

Kerro’s team found something surprising in the lab. As expected, many subjects burned more calories during the extracurricular activity, but decreased energy expenditure during the rest period. In other words, when we move more, the body compensates for this additional need for energy by reducing its basal metabolic rate.

Compensation increases with obesity

What is even more interesting, however, is that this balance occurs at a higher percentage in obese people. In overweight subjects, the resting metabolic rate fell by almost half (49 percent) for each calorie burned. In contrast, it means: for every calorie burned, the body saves half a career at resting metabolic rate.

Researchers report that people who have more body fat may change the way their bodies use calories to compensate for the extra food intake. This finding may explain why some people are more obese than others despite similar levels of activity – and why they often fail to lose weight. “It seems that the metabolism of people with more body fat either compensates for the extra expenditure in the first place, or that this compensation leads to more weight gain,” Kerro says.

Counting calories makes sense, exercise can be counterproductive

The results confirm that obese people find it much harder and harder to lose weight than other people. “The bodies of obese people appear to be particularly effective at storing fat stores,” says co-author John Speakman. “For some unfortunate people, if they exercise too much it can cause them to gain weight rather than lose it.”

It is still unclear what mechanisms are behind this increased compensation. But if this energy compensation has a genetic basis, it may be possible to screen overweight people for it in the future, the researchers conclude.

current biology; DOI: 10.1016/j.cube.2021.08.016