How does exercise affect weight loss?

Exercise is an advantageous adjunct to diet for achieving and maintaining weight loss, although exercise alone is an inefficient way to induce significant weight loss.^[1][2] An umbrella review published in 2021 reported that an exercise program (60–440 minutes of exercise per week, average of 150–200 minutes per week) induces an average weight loss of 1.5–3.5 kg, with aerobic exercise being much more effective than resistance exercise.^[3] Also, resistance exercise can reduce muscle loss associated with weight loss, which is important for preserving metabolic rate and aesthetic goals.

High volumes of exercise (225–400 minutes or 2,000 kcal per week) can induce clinically significant weight loss (at least 5% of initial body weight),^[2] but there are potential limitations to performing even higher volumes of exercise to induce further weight loss.

The traditional view assumes that increasing exercise leads to a corresponding increase in total energy expenditure, facilitating greater amounts of weight loss. However, more recent evidence suggests that there is a plateau in total energy expenditure at high levels of physical activity,^[4][5][6] meaning that exercising more leads to a corresponding increase in total energy expenditure up to a point. Beyond this threshold, each additional increment of exercise contributes less and less to total energy expenditure. This phenomenon, known as “energy compensation”, varies in magnitude between individuals, and seems to affect men and women of all ages similarly.^[5]

While the precise mechanisms are not entirely clear, energy compensation is a product of behavioral and physiological adaptations. Behavioral adaptations include decreases in nonexercise activity thermogenesis (e.g., less fidgeting, increased sitting), whereas physiological adaptations include downregulation of immune activity, hypothalamic-pituitary-adrenal axis and sympathetic nervous system activity and reactivity, and reproductive function.^[7]

The optimal strategy for promoting weight loss is a combination of a hypocaloric diet and adequate amounts of exercise (i.e., enough to facilitate the rate of weight loss the individual is pursuing while maintaining muscle mass). High volumes of exercise are also pivotal for maintaining weight loss.^[8]