Why exercise is more important than ever when taking weight-loss drugs

For decades, conventional wisdom held that, to lose weight, you must eat less and move more. Of course, that is easier said than done, which is why drugs like Wegovy are so revolutionary. By suppressing appetite, they help tackle the first part of that equation, typically leading to dramatic weight loss. But what about the second? Do we still need to hit the gym if weight-loss drugs are causing the number on the scales to drop? And what impact do these drugs have on our ability to exercise?

What is becoming clear is that exercise may be even more crucial for people who are on these medications than it is for those who aren’t. The ability of semaglutide to induce rapid weight loss (see “How they work”, below) also leads to notable declines in muscle mass. For instance, a 2021 study of 95 people who were overweight or had obesity and were taking semaglutide found that lean body mass decreased by almost 10 per cent, on average, after 68 weeks.

Lean body mass encompasses body tissues like muscle and bone. So, these results suggest that both deteriorate when taking weight-loss drugs, says Signe Sørensen Torekov at the University of Copenhagen. Because these drugs lead people to consume fewer calories, the body must break down fat, muscle and even bone for nutrients.

“Our understanding is that up to about 40 per cent of the overall weight loss that is seen from semaglutide is thought to be potentially from the loss of muscle mass,” says …