People on weight loss drugs reduce their activity levels, according to a team at St John’s Hospital Illinois

People taking weight loss medications such as Ozempic, Wegovy, Mounjaro and Zepbound may be losing weight, but they’re also becoming less physically active, according to new research presented at the ENDO 2026 annual meeting of the Endocrine Society.

Researchers analysed wearable activity data from 753 adults with obesity, who had started taking the drugs, using electronic health records and Fitbit data from the US National Institutes of Health’s All of Us research programme.

Participants were predominantly women (78.6 per cent) and an average age of 52.7 years-of-age.

The study found average daily step counts fell from 5,047 to 4,487 after participants started the medication, while time spent in moderate-to-vigorous physical activity dropped from 28 minutes a day to 22 minutes. The biggest reductions were seen in men and in people experiencing joint or muscle pain.

The findings challenge the assumption that losing weight leads people to become more active. Instead, researchers suggest that although the drugs are highly effective at reducing body weight, they do not automatically encourage healthier movement habits and may even contribute to a decline in everyday activity.

Exercise can’t be optional for people taking weight loss drugs. They need targeted interventions that encourage physical activity

The trend is concerning because these drugs are known to reduce lean body mass as well as fat, making resistance training and regular physical activity important for preserving muscle, connective tissue, strength and long-term physical function. Research has also shown that exercise can help maintain metabolic health and improve the durability of weight loss after treatment.

Importance of structured exercise

Lead researcher Dr Sajana Maharjan of HSHS St John’s Hospital in Springfield, Illinois, said: “While many assume that weight loss leads naturally to increased physical activity, our study suggests otherwise. The findings reinforce that exercise cannot be optional for people taking these medications. People need targeted interventions that encourage physical activity alongside medication for obesity.”

The researchers say this is the first large-scale study to use wearable fitness tracker data to examine changes in physical activity among people taking weight loss drugs. They conclude that structured exercise programmes should be integrated into obesity treatment, creating a significant opportunity for health clubs, personal trainers and exercise professionals to support people using weight-loss medications while helping them protect muscle mass and maximise long-term health outcomes

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