Experts warn weight-loss jabs such as Wegovy and Mounjaro could worsen bone health in menopausal women already at risk of osteoporosis.

Dr Jack Mosley, son of the late broadcaster and health advocate Michael Mosley, said the treatments may carry hidden side-effects for women with fragile bones.

The drugs mimic GLP-1, a natural hormone that increases insulin, slows digestion and reduces appetite. While trials show strong weight-loss results, rapid weight reduction can worsen osteoporosis – a condition that leaves bones brittle and prone to fracture.

Speaking on The Dr Louise Newson Podcast, Dr Mosley said: “We know one of the risks of GLP-1s is that a significant amount of the weight you lose is muscle or lean body mass… 25–40 per cent of the weight you lose is body mass.

“And a main component of that is muscle. And muscle is so important for longevity and living healthy independent life in later age.

“I do also have some concerns it could, in certain people who aren’t eating the right nutrition, it could actually potentially exacerbate things like osteoporosis in menopausal women.

“That period around menopause and perimenopause, your hormones completely change and the decline in oestrogen and testosterone and progesterone can have big effects on you, especially in body composition… muscle loss can accelerate and other things like osteoporosis. So we really need to approach them with knowledge and care.”

Dr Mosley said GLP-1 drugs were “powerful” but “not magic bullets” in the battle against obesity.

Common side-effects include nausea and diarrhoea, with some patients developing serious complications such as pancreatitis or allergic reactions.

Dr Martin Whyte, associate professor of metabolic medicine at the University of Surrey, said it was “not proven” that GLP-1s themselves reduce bone mineral density.

“In fact, some studies suggest these drugs may have protective effects on bone,” he said.

“Major trials found no increased risk of fractures. However, a key complicating factor is that weight loss – regardless of the cause – can increase the risk of low bone density, especially when it occurs rapidly.

“This happens because weight loss reduces the mechanical load on bones and alters the hormonal signals that regulate bone maintenance. Regular exercise, by increasing mechanical load, can help counteract the effects of weight loss on bone health.”

Around 1.5m Britons are now paying privately for weight-loss jabs, while NHS provision remains limited.

The drugs have also gained celebrity endorsement, with former tennis champion Serena Williams appearing in an advertising campaign.

Dr Mosley raised concern over a lack of awareness about the risks: “People are not provided with information about these medications.

“They are very effective but a lot of people don’t understand the risks and rewards, the side effects and how to manage them.”

Stephen Lawrence, a GP and associate clinical professor at the University of Warwick, said GLP-1 drugs were “powerful medical tools with clear benefits for some, but also real risks, especially muscle loss and potential nutritional problems, if used without lifestyle changes or medical oversight.”

“They are much more than magic bullets and should be approached thoughtfully, respecting both their potential and their limits,” he said.

“Menopause is a time of significant metabolic change, and while GLP-1 medications and hormone therapy both have roles in managing weight and health for women in this phase, they are most effective and safest when used as part of a broader lifestyle plan that includes exercise and nutritional support.

“Individualised care and evidence-based medical advice should always guide choices around these medications.”

Professor Lawrence added that women accessing the drugs on the black market faced greater risks.

Dr Mosley clarified that he was “not for or against” weight-loss jabs, adding: “They can be really beneficial for certain people, who are living with obesity and have tried a lot of these other dietary options. It is very difficult for some people.”