Research from the University of Oxford has found people on weight loss drugs revert to their original weight after 10-20 months, making it vital we champion the role of exercise and behaviour change

When weight loss drugs hit the market, clinical trials showed their use led to loss of muscle mass unless the user exercised, yet the only reference to this came in the small print, along with the contra-indications, leaving consumers unaware of the trap they were walking into.

It quickly became clear that up to 40 per cent loss of muscle mass was being experienced if people took the drugs without exercise, with an impact on heart muscle.

Now, research from the University of Oxford has found weight loss which occurs as a result of drug use is not as enduring as that achieved by conventional dieting.

Bearing in mind the clinical limit of two years for taking weight loss medication, the research team found people returned to their original weight between 10 and 20 months after stopping injections, depending on the drug. This contrasts with 60 months with conventional dieting.

The difference is attributed to the fact that taking weight loss drugs doesn’t require behaviour change, so people revert as soon as the drugs are stopped.

People studied lost an average of 8kg on older-style drugs and 16kg on newer ones, such as Wegovy (semaglutide) and Mounjaro (tirzepatide), regaining all the weight in 10 months after the use of the older drugs and 20 months after the newer, stronger ones.

This new insight must change the way we approach the optimisation of weight loss drugs, while the overall response to this news – with its lack of reference to the importance of exercise – is concerning.

We can run a doom scenario where the worst outcome for people on these drugs – who do not exercise – will be to lose muscle mass and heart muscle and then regain their body mass with a greater proportion of body fat within a year or two.

They will have less energy-producing lean muscle tissue, meaning their metabolic rate will drop, so they will not be able to consume so many nutrients.

There will also be a greater burden on a weakened heart, less resilience, less stable joints and rapidly accelerated physiological ageing.

If this outcome transpires, within as little as two years we’re likely to have a growing cohort of people who are experiencing rapid ageing and a whole raft of metabolic and heart-related health issues and reduced quality of life.

The industry must step up to be part of the solution to this, to help individuals and society avoid catastrophic outcomes at a time of falling health budgets.