Obesity rates have soared in recent years. Between 1990 and 2022, the number of adults living with obesity worldwide more than doubled (World Health Organization, 2025). Now injectable weight loss drugs are changing the clinical landscape, helping many people achieve dramatic weight loss.
In the UK, it’s estimated that about 1.5 million people are currently using these medications, with many buying them without full medical supervision (Triggle and Roxby, 2025), as would be recommended by NICE (2025a) and the Medicines and Healthcare products Regulatory Agency (see Statistics, overleaf).
“A lot of patients in my practice are taking these medications for both medical and cosmetic reasons. I suspect their use will increase rapidly over the next few years,” says John Rose MCOptom, owner of John Rose Eyecare in Surrey, and a founding member of the European Academy of Optometry and Optics.
“We are all aware that being morbidly obese or even moderately overweight is a risk factor for ill health and that ‘fat’ is inflammatory. Any weight loss is beneficial to health.”
The European Association for the Study of Obesity now recommends the weight loss injections semaglutide (Ozempic or Wegovy) and tirzepatide (Mounjaro or Zepbound) as first-line treatment for people living with obesity and related conditions (EASO, 2025).
Semaglutide and liraglutide (Saxenda or Victoza) are GLP-1 receptor agonists (GLP-1 RAs). They mimic the hormone glucagon-like peptide-1 (GLP-1), which helps people feel fuller for longer, reduces appetite, slows digestion and increases insulin production to regulate blood glucose levels (British Heart Foundation, 2025).
Tirzepatide targets two hormones, GLP-1 and glucose-dependent insulinotropic polypeptide (GIP). These drugs differ in dose, formulation and who can take them. Liraglutide can be prescribed to children aged 12 to 17 years without type 2 diabetes and from age 10 for those with type 2 diabetes (London Obesity Clinic, 2024).
Since March 2025, GPs in England can prescribe tirzepatide to adults living with obesity who have at least four of five weight-related problems – dyslipidaemia, hypertension, obstructive sleep apnoea, cardiovascular disease and type 2 diabetes – with a body mass index of 40 or higher (NHS England, 2025).
These drugs all share similar side effects, including pancreatitis and gall bladder problems, along with shorter-term gastrointestinal issues such as nausea, vomiting, diarrhoea, constipation and abdominal pain and bloating, gastro-oesophageal reflux and hypoglycaemia (London Obesity Clinic, 2024).