Orlistat
Orlistat is a weight-loss medication that blocks the absorption of about a third of the fat you eat, helping create the calorie deficit needed to lose weight.
Plain English
Patient-Friendly Explanation
Orlistat is a weight-loss medication that works inside the digestive tract rather than in the brain. It blocks an enzyme called lipase so that roughly a third of the fat from a meal passes through the body unabsorbed instead of being stored. Because less dietary fat is absorbed, the medication helps create the calorie deficit needed to lose weight, but it works best when combined with a lower-calorie, lower-fat eating plan. Unlike many other weight-loss medications, it does not work by suppressing appetite.
Medical
Clinical Definition
Orlistat is a reversible inhibitor of gastric and pancreatic lipases that reduces dietary triglyceride hydrolysis, decreasing fat absorption by approximately 30%. In randomised controlled trials it produces modest weight loss (roughly 2–3 kg more than placebo at one year) with small improvements in LDL cholesterol, blood pressure and glycaemic control. Adverse effects such as oily spotting, steatorrhoea, faecal urgency and flatulence with discharge reflect unabsorbed fat and worsen with high-fat meals; absorption of fat-soluble vitamins (A, D, E and K) can be reduced, so supplementation is commonly advised. It is contraindicated in chronic malabsorption syndrome and cholestasis and is not recommended in pregnancy.
Key Insight
Why It Matters
Because orlistat makes very fatty meals unpleasant to eat, it can double as a practical teaching tool for learning to recognise hidden fats. In our weight management programme we review diet, fat-soluble vitamin status and progress together so that any medication is used safely and effectively as part of a complete plan.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: September 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
