Medicines for weight management: what's available and how they work

Semaglutide, tirzepatide and liraglutide mimic gut hormones that signal fullness and slow stomach emptying. Tirzepatide also acts on the GIP receptor. They're mostly given as injections, daily or weekly; semaglutide is also available as a tablet.

They're the best-studied group in this area. The most common side effects are gastrointestinal, especially during titration. Whether and how a switch or a dose change happens is decided by the doctor in each individual case.

Orlistat blocks an enzyme in the gut that breaks down fat, so part of dietary fat passes through undigested. Oily stools and diarrhoea are typical, especially after fatty meals. A lower-dose version is available over the counter in pharmacies.

The combination of naltrexone and bupropion acts on appetite and reward centres in the brain. It's prescription-only and has its own contraindications, for example certain mental health conditions or high blood pressure.

Fibre supplements, fat binders, “metabolism boosters” and slimming patches are widely advertised. For most there's no or only weak evidence of a meaningful effect. Fibre can support fullness but doesn't replace treatment.

Be careful with online products promising “fast weight loss”: they can contain undeclared, sometimes dangerous substances.

Prescription weight-management medicines are usually approved for adults with a BMI of 30 or more, or 27 or more with a weight-related condition. They're meant as an addition, not a replacement for diet, movement and sleep.

Whether a medicine is an option for you is assessed in the medical review of your questionnaire.

This Journal article offers general information. It is not a diagnosis, a prescription or a promise of any result. Whether treatment is suitable for you is decided by a doctor after reviewing your questionnaire. For acute or severe symptoms, contact your GP, the out-of-hours medical service (116117) or, in an emergency, 112. Whether and how a switch or a dose change happens is decided by the doctor in each individual case.