Obesity is associated with significant morbidity and has substantial healthcare implications, with current projections estimating that by 2030 obesity will cost the NHS approximately pounds 2 billion each year. Lifestyle modification remains the cornerstone of anti-obesity treatment, but drugs can be introduced as adjuncts to assist and maintain weight loss. At present, the lipase inhibitor orlistat (Xenical) is the only UK-approved long-term medical therapy for obesity. Double-blind clinical trials have shown that orlistat significantly increases weight loss compared to placebo, but the array of adverse side effects associated with orlistat limits its tolerability. The need for more effective and better-tolerated anti-obesity medications is clear and six therapies have reached phase-III trials.