People on GLP-1 drugs like Ozempic moved less, new study finds

GLP-1 receptor agonists, the drug class that includes semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound), have delivered effective weight loss for millions worldwide. But a new study summarised by Science Daily finds that people taking these drugs significantly cut their daily physical activity, reigniting the debate over how much of the lost weight is fat, and how much is muscle.

The study tracked GLP-1 users' step counts, average movement intensity per minute, and weekly moderate-to-vigorous activity. The authors report a measurable decline in daily movement within the first three months of treatment. The drop was visible in both previously active and previously sedentary participants.

Researchers attribute the trend to two main mechanisms. The first is appetite suppression. Because GLP-1 drugs act on hunger and satiety centres in the brain, people eat less and energy expenditure declines accordingly. The second is fatigue and mild muscle weakness. The drugs' side-effect profile, especially in early weeks, includes nausea and low energy, which can push people away from exercise.

The most clinically significant consequence is that muscle-mass loss can account for as much as half of total weight lost. Earlier analyses of phase 3 trial data signalled the same pattern. Muscle matters not just for strength or appearance: it is critical for glucose metabolism, basal metabolic rate, balance and fall prevention. The longer-term consequences of muscle loss are particularly significant for patients over 60.

For that reason, new clinical guidance recommends that GLP-1 treatment be delivered alongside a structured exercise programme. Resistance (strength) training is the unambiguous priority: sessions of 30 to 45 minutes targeting major muscle groups at least twice a week measurably reduce muscle loss in patients on the drugs. Low-impact aerobic activity, like walking, cycling or swimming, supports daily energy expenditure.

A second recommendation is adequate protein intake. Nutritionists suggest GLP-1 patients aim for 1.2 to 1.6 grams per kilogram of body weight each day, spread across three or four meals. With reduced appetite, liquid protein, eggs, fish and legumes are practical ways to reach those targets.

The study suggests users are not so much "forgetting" to move once they start the drug; movement becomes harder. The clinician message is straightforward: keeping a slimming body in motion is the key way to balance the side effects that come with the drug's benefits.

Observations that weight tends to return when treatment is stopped reinforce the point. Exercise habits built at the start of treatment make it easier to retain muscle and metabolic resilience when the drug is discontinued.

Clinicians also encourage open dialogue between patients and their doctors: the exercise plan should be tailored to personal medical history, with input from a physiotherapist or exercise physiologist if heart disease, orthopaedic issues or balance problems are present. GLP-1 drugs are powerful, but used alone, they may not deliver their full potential.

This article is not medical advice. For questions about GLP-1 drugs and exercise planning, consult your own clinician.