New research may help solve the problem of why many people who increase their activity fail to lose weight. Although exercise burns calories, previous studies have shown that many people compensate for the increased activity by eating and resting more, thus negating some potential weight loss benefits. But “basically, this study disproves the notion that the more you exercise, the more you compensate and the less weight you actually lose,” said lead study author Kyle Flack, PhD, RD, assistant professor in the Department of Dietetics and Human Nutrition at the University of Kentucky in Lexington.
Investigators tackled this question by randomly separating 29 sedentary men and women with overweight and obesity into two groups for 12 weeks of training. One group burned 1,500 exercise calories per week by training for about 30 minutes 5 times per week. The second group trained for about an hour 5 times per week, for a total of 3,000 exercise calories per week. Investigators measured resting metabolic rate, body composition and dietary intake both before and after the program. All participants wore activity trackers.
Data analysis showed that members of the first group lost little if any body fat. In contrast, most people in the second group did lose weight, and 12 out of 15 lost at least 5% of their body fat. Study authors found that compensatory mechanisms of increased eating and resting were not proportional to the amount of energy expended. In fact, members of both groups made similar lifestyle adjustments in response to the increased activity.
Flack said, “Regardless of how much exercise you do, you will compensate similarly—a little over 900 kcal per week—so we better exercise more to make up for it, if we want to lose weight. Fifteen hundred calories per week was not enough exercise, but 3,000 was.”
The study is available in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology (2018; doi:10.1152/ajpregu.00071.2018).