Peripherally acting antiobesity drug – intestinal lipase inhibitor
ATC code: A08AB01 (Orlistat)
Brand names
Xenical, Alli, Orlistat Stada
Orlistat covalently binds the active site of gastric and pancreatic lipases in the small intestine – blocks dietary triglyceride hydrolysis to free fatty acids and monoglycerides. About 30% of dietary fat at the standard 120 mg three-times-daily dose is not absorbed and is excreted in feces. Systemic absorption of orlistat is minimal (<1%). Effect is on dietary fat only; no impact on carbohydrates or protein.
Second line
Obesity with BMI ≥30 or BMI ≥27 with risk factors (type 2 diabetes, dyslipidemia, hypertension) when 6 months of lifestyle modification have not produced ≥5% weight loss. Per EASO 2024 and SEEN 2023 – second-line after diet, physical activity, and behavioral therapy. Dose: 120 mg three times daily with or within one hour of a fat-containing meal. Skip the dose if the meal is fat-free. Effect at 4-6 weeks; discontinue if weight loss <5% by 12 weeks.
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Orlistat is heavily marketed to non-obese people for quick weight loss, summer weight loss, and healthy weight loss at BMI 25-27. Per EASO 2024 and SEEN 2023, neither weight above ideal at BMI <27 nor cosmetic weight loss is an indication. Without concurrent dietary fat restriction the drug does not work; with more than 30 g of fat per meal it causes marked steatorrhea, fecal incontinence, and flatulence. Long-term use without monitoring risks deficiency of fat-soluble vitamins A, D, E, K and reduced bone mineral density. If prescribed at BMI <27 without mandatory dietary changes, consider getting a second opinion and reconsider whether you need this drug at all.
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Contraindicated. Safety not studied; theoretical reduction of fat-soluble vitamins may affect fetal development.
Contraindicated. Theoretical reduction of fat-soluble vitamins is undesirable for the infant via milk.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Orlistat is evaluated for the following indications with varying evidence strength: Obesity (evidence tier B), Anti-aging and longevity (evidence tier D). See the full indication matrix with dosing and citations above on this page.
Common side effects of Orlistat (≥ 1 in 100): Steatorrhea and oily stools, Frequent defecation, Flatulence with discharge, Abdominal pain and cramping, Fecal urgency. See the Safety section for uncommon and serious reactions.
FDA category X. Contraindicated. Safety not studied; theoretical reduction of fat-soluble vitamins may affect fetal development.
Contraindicated. Theoretical reduction of fat-soluble vitamins is undesirable for the infant via milk.
Orlistat is contraindicated in: Hypersensitivity; Malabsorption syndrome; Cholestasis; Pregnancy and breastfeeding; Children under 12. Full list in the Safety section.