The landscape of weight management medication in the UK has changed dramatically in recent years. The arrival of GLP-1 receptor agonists — particularly semaglutide (Wegovy/Ozempic) and tirzepatide (Mounjaro) — has produced the most effective pharmacological weight loss interventions ever approved, fundamentally shifting how obesity medicine is practised.
Orlistat: The Established OTC Option
Orlistat (Alli, 60mg OTC; Xenical, 120mg prescription) is the only weight loss medication available OTC in the UK. It works by inhibiting pancreatic lipase — reducing fat absorption by approximately 30%. Average weight loss: 5–7% of body weight over 1 year (approximately 3–4kg more than placebo). OTC availability (Alli 60mg): BMI ≥28 in adults 18+. Side effects are the main limiting factor: fatty stools, oily leakage, urgency, and faecal incontinence — driven by unabsorbed fat passing through the bowel. These are substantially reduced by following a low-fat diet. Fat-soluble vitamin supplementation (A, D, E, K) is advised during use. Significant drug interactions: cyclosporine and some HIV medications — check with pharmacist.
GLP-1 Receptor Agonists: The New Generation
GLP-1 (glucagon-like peptide-1) is a gut hormone released after eating that stimulates insulin secretion, suppresses glucagon, slows gastric emptying, and — crucially — acts on hypothalamic appetite centres to produce profound reductions in hunger and food intake. Injectable GLP-1 receptor agonists mimic this effect at pharmacological doses. Semaglutide (Wegovy): NICE-approved in June 2023 for obesity management via NHS specialist services. Average weight loss in the STEP trials: approximately 15% of body weight over 68 weeks — an unprecedented outcome for a non-surgical intervention. Available privately from UK licensed prescribers. Tirzepatide (Mounjaro): dual GIP/GLP-1 receptor agonist. Average weight loss in SURMOUNT trials: approximately 20% of body weight — the most effective currently approved pharmacological treatment for obesity. NICE appraisal completed 2024. Side effects of GLP-1 agonists: nausea, vomiting, diarrhoea (typically transient, reducing with gradual dose escalation); pancreatitis (rare); contraindicated in personal/family history of medullary thyroid carcinoma.
Who Qualifies
NHS specialist weight management services: BMI ≥35 (or ≥30 with weight-related comorbidities) plus failure of lifestyle interventions. Private prescription: more accessible — typically BMI ≥30 or ≥27 with comorbidities, prescribed by licensed UK prescribers. All weight loss medications are intended as adjuncts to dietary and lifestyle modification — not substitutes for them.
Frequently Asked Questions
Is Ozempic the same as Wegovy?
Both contain semaglutide, but Ozempic is licensed for Type 2 diabetes management (approved doses up to 1mg injection weekly) while Wegovy is licensed specifically for obesity (doses up to 2.4mg weekly). Using Ozempic off-label for weight management without diabetes is prescribable by doctors but is not an approved indication — Wegovy is the appropriate licensed option for obesity.
Will I regain weight when I stop GLP-1 medication?
Yes — the evidence shows significant weight regain when semaglutide is stopped. This reflects that the medication is treating the underlying biology of obesity and its effects cease when the drug is stopped. Long-term or indefinite use is increasingly recognised as the appropriate model for pharmacological treatment of obesity, similar to long-term antihypertensive or statin therapy.
Speak to our pharmacist at Huncoat about OTC Alli (orlistat) and accessing prescription weight management services. Related: Weight Loss Guide, Pre-Diabetes.
At Huncoat Pharmacy: Weight loss injection service – Mounjaro & Wegovy, Private prescription service, Book a weight loss consultation.