Senior medics are sounding the alarm over the hidden health risks of weight loss jabs after new research reveals the blockbuster drugs strip away not just fat but vital muscle and bone mass.
The Royal Osteoporosis Society is among those expressing concern over the evidence which warns up to 40 percent of the weight loss while using GLP-1 “skinny jabs” – such as Ozempic, Wegovy and Mounjaro – includes loss of vital bone and muscle.
They warn loss of muscle can impair strength, blood sugar levels as well as joint stability while loss of bone density raises the potential deadly risk of fractures and osteoporosis, particularly in later life.
Women are at higher risk of osteoporosis, especially after menopause, when hormone levels drop. Experts say stripping away additional bone mass through rapid weight loss could be a silent recipe for disaster, increasing the risk of fractures, hip injuries, and long-term disability.
Julia Tompson, Royal Osteoporosis specialist nurse said: “This is an emerging field of research and people need to be warned that using these drugs increases the risk of losing bone and muscle as well as fat. Bone and muscle health is key to prevent the risk of falling and fractures which can lead to premature death or else have a devastating effect on people’s ability to live independently.”
She added: “It is essential that these drugs are prescribed appropriately with full honest discussion with a doctor and with proper ongoing support once they are prescribed.”
Professor Carl Heneghan, Director of Oxford University’s Centre for Evidence Based Medicine who has examined the data said: “Any drug that reduces muscle mass and bone density is a bad idea for people who are vulnerable to frailty, fracture and osteoporosis.”
He added: “Anyone trialling these drugs has to weigh up the risks and benefits of these drugs with their GP. The evidence is clear that these drugs carry significant risks and the longer a patient stays on them the greater the risk. I am always concerned about medicating large swathes of the population as a simple fix. This is normalising obesity and not a way for society to resolve problems.”
A recent analysis from leading physiotherapy lecturer Dr Jennifer James at the University of Liverpool, warned up to 40 percent of the weight lost while using GLP-1 is muscle and bone.
And a separate analysis in the Lancet concluded that 25-39 percent of the weight lost with the jabs is linked to lost bone or muscle density. The research concluded: “…the decline in muscle mass with GLP-1 receptor agonists is several times greater than what would be expected from age-related muscle loss…”
Approximately 500,000 people in the UK take GLP-1 weight loss drugs. And it is estimated up to 95 percent are buying the drugs privately, many through online pharmacies where checks are not always as rigourous.
Professor Francesco Rubino, an expert in obesity at Kings College Hospital said: “There is an increased risk that buying these drugs privately online is that these kinds of complications may not be properly considered as patients can circumvent the proper checks. These drugs carry risks – and any trade off should make sense and be balanced with each patient.”
Manel Riera, an obesity expert at the Royal Shrewsbury Hospital said: “We do not have long term data on these drugs to establish the full risks and benefits. There are patients who are taking these drugs privately without proper supervision and while they can be useful for some people for others they need to be taken under proper supervision to ensure they do not do more harm than good.”
Dr Alison Cave, Chief Safety Officer of the drug regulator the Medicines and Healthcare products Regulatory Agency (MHRA) said: “Our role is to continually monitor the safety of medicines during their use, including GLP-1 receptor agonists (RAs). When a safety issue is confirmed, we always act promptly to inform patients and healthcare professionals and take appropriate steps to mitigate any identified risk.
“New medicines, such as GLP-1 RAs, are more intensively monitored to ensure that any new safety issues are identified promptly.
“On the basis of the current evidence, the benefits of GLP-1 RAs outweigh the potential risks when used for the licensed indications. The decision to start, continue or stop treatments should be made jointly by patients and their doctor, based on full consideration of the benefits and risks.
A spokeswoman for Eli Lilly which makes Mounjaro said: “The MHRA – like other regulators throughout the world, who assess the risks and benefits of medications – authorised tirzepatide (Mounjaro) for use both to treat type 2 diabetes and for weight management.
Mounjaro should only be used when prescribed by a healthcare professional and prescriptions should be fulfilled and supplied by reputable pharmacies and providers. It is important for patients to maintain a balanced diet and engage in regular physical activity to support overall health, including bone and muscle maintenance.”
She added: “With regard to lean muscle mass, Lilly’s SURMOUNT 1 phase 3 clinical trial showed that patients treated with tirzepatide had approximately three times more fat-mass reduction than lean-mass reduction and experienced an overall improvement in body composition. The ratio of fat-mass loss to lean-mass loss was similar to that reported in lifestyle-based treatments for obesity. “
A spokeswoman for Novo Nordisk said: “Novo Nordisk, the manufacturer of Ozempic – (must keep) prescribed for diabetes and also Wegovy – licenced for weight loss – confirmed that the impact on muscle mass was not specifically studied in clinical trials.
She added that in a “sub-study” of 140 patients bone scans showed patients on the drug lost more fat than bone or muscle.
She added: “To minimise the loss of lean tissue, a combined approach involving healthy diet and physical activity is essential—something that aligns with the recommended use of Wegovy.”
Researchers aren’t completely sure why people lose muscle and bone during weight loss.
One theory is that during weight loss, muscle proteins are broken down faster than they can be built. And, because there’s less stress on the bones due to lost weight, this might affect normal bone turnover – the process where old bone is removed and new bone is formed leading to less bone mass being manufactured than before weight loss.