Orlistat and other older weight-loss medicines explained

Orlistat blocks lipase, an enzyme that digests dietary fat, so a proportion of the fat eaten passes through undigested. It is taken with main meals that contain fat, and a dose is skipped if a meal is missed or contains no fat. It does not act on appetite, so it suits people who want a non-injectable option and can follow a lower-fat eating pattern.

Because undigested fat passes through the bowel, common effects are oily or loose stools, urgency, wind and sometimes leakage. These are worse after high-fat meals, which teaches many people to eat less fat. Orlistat can reduce absorption of fat-soluble vitamins, so a multivitamin taken at a different time of day is often suggested. It can interact with some medicines, including ciclosporin, levothyroxine and warfarin, so a pharmacist should check your medicines. It is not suitable for everyone, including people with chronic malabsorption or gallbladder problems.

Liraglutide is a daily injectable GLP-1 medicine with a weight-management licence. Its mechanisms and side effects resemble those of the newer weekly injections, but weight loss in trials was lower. NICE has appraised it for use in specialist services. Many patients and clinicians now prefer weekly products where they are available, but supply and local policy vary.

A combination of naltrexone and bupropion has a licence for weight management in the UK, though NHS availability is limited. Older appetite suppressants were withdrawn for safety reasons, and the MHRA warns about illicit products sold online that contain unlicensed or banned substances. Do not buy weight-loss tablets from unregulated sites.

People who dislike injections, who cannot access or tolerate newer medicines, who have a moderate need and prefer a lower-intensity approach, or who are planning pregnancy and want a short-term option that clears quickly. Orlistat is not usually advised in pregnancy but acts locally rather than being absorbed. Decisions are individual and a clinician can advise.

Many people do better by starting with a lower-fat pattern of eating a few days before the first capsule, carrying spare underwear and a pad in the early weeks and keeping a small food and symptom note. If side effects are intolerable after a fair trial, stopping is reasonable. A pharmacist can check your other medicines before you start and explain the multivitamin timing.