The number one workout rule everyone on GLP-1s should follow, according to a doctor

It’s not an overstatement to say that GLP-1 medications have revolutionized weight loss.

GLP-1 medications work by mimicking glucagon-like peptide-1, a hormone released from the gut after eating, which regulates blood sugars and appetite.

This means that people often feel full sooner, stay satisfied longer between meals and think less about food, explains Dr Kim Boyd, chief medical officer for Weight Watchers.

“GLP-1 medications work by regulating several systems that influence appetite and metabolism,” she says. “They activate receptors in the pancreas when blood glucose levels rise to increase insulin and reduce glucagon, which helps keep blood sugar levels steadier after meals.

“At the same time, they act on appetite centers in the brain to reduce hunger and cravings, and they slow stomach emptying so people feel full sooner and stay satisfied longer. Together, these effects help regulate appetite, stabilize blood sugar, reduce cravings and help address the biology of obesity,” says Boyd.

GLP-1 medications can be so effective at helping you lose body mass, you may well lose significant amounts of lean mass (anything that’s not body fat) along the way.

A recent meta-analysis of studies into the medication and its effects showed that lean mass loss typically accounted for 20-30% of total weight lost, although this percentage varies depending on the study and method used to measure body composition.

That’s a problem because that reduction in lean mass will include muscle.

“Losing too much muscle can reduce metabolic rate and make it harder to maintain weight loss over time,” says Boyd.

That’s one major reason why Weight Watchers has recently collaborated with fitness app Pvolve to offer on-demand home strength workouts to members.

“The goal isn’t just weight loss—it’s improving the composition of that weight loss by prioritizing fat loss while protecting muscle, strength and metabolic health. That’s why we encourage people taking GLP-1s to pair the medication with habits that help protect lean mass, including regular strength training and adequate protein.”

So while it might be tempting to skip the strength training and just try and eat less, it could slow your metabolism, says Boyd.

“If someone only reduces calories without strength training, the body often adapts by becoming more energy efficient,” says Boyd. “Over time, that can mean burning fewer calories at rest, in part because of reductions in lean mass, which may make weight maintenance more difficult.

“That’s one reason the traditional dieting advice of simply ‘eating less and exercising more’ without attention to food quality or the type of exercise performed often falls short for long-term health. Muscle is also a key factor in long-term health, strength, and vitality as we age.”