Last verified: 17 days ago
Orlistat
Also known as: Xenical, Alli, tetrahydrolipstatin, THL
Evidence under review. — Not yet rated
FDA-approved fat-blocker that reduces dietary fat absorption to support weight loss in adults and teens.
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What it does
Orlistat is an FDA-approved weight-loss drug that works by blocking pancreatic and intestinal lipase enzymes, preventing your gut from absorbing roughly one-third of the fat you eat. The...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
120 mg three times daily (prescription); 60 mg three times daily (OTC)
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Found in
What the Science Says
Orlistat is an FDA-approved weight-loss drug that works by blocking pancreatic and intestinal lipase enzymes, preventing your gut from absorbing roughly one-third of the fat you eat. The unabsorbed fat passes out of the body in stool. Clinical trials show it produces around 5–8% body weight loss over 6 months when combined with diet and lifestyle changes. It has also been studied in adolescents with obesity, where it produces modest but potentially meaningful reductions in BMI.
What It Doesn't Do
Not a magic pill — it only blocks fat, not carbs or sugar. Won't work without dietary changes. Not a cancer treatment, despite some early lab research. Doesn't eliminate the need for lifestyle modification. Won't produce dramatic weight loss on its own.
Evidence-Based Benefits
Produces around 5–8% body weight loss over 6 months when combined with diet and lifestyle changes.
Moderate EvidenceEffective at: 120 mg three times daily
Supporting studies (click to view on PubMed):
Reduces BMI in adolescents with obesity when added to behavioral interventions.
Moderate EvidenceEffective at: 120 mg three times daily
Supporting studies (click to view on PubMed):
Increases fecal fat excretion from roughly 4% to 13–14% of dietary fat intake.
Moderate EvidenceEffective at: 120 mg three times daily
Supporting studies (click to view on PubMed):
Produces small improvements in blood glucose and lipid markers alongside weight loss.
Weak EvidenceEffective at: 120 mg three times daily
Supporting studies (click to view on PubMed):
Absorption & Bioavailability
Poor systemic absorption — intentional by design. Orlistat acts locally in the gut. Peak plasma concentrations stay below 5 ng/mL. Minimal systemic exposure confirmed across multiple formulations.
Red Flags to Watch For
- High-dose animal studies showed dose-related liver and kidney damage — monitor liver and kidney function during use
- Oily, greasy stools and fecal urgency are common and can be socially disruptive
- Blocks absorption of fat-soluble vitamins (A, D, E, K) — supplementation is recommended
- Not appropriate for people with chronic malabsorption syndrome or cholestasis
- Long-term safety data in children and adolescents is limited
Products Containing Orlistat
See how Orlistat is used in these analyzed products:
Frequently Asked Questions
What does Orlistat do?
FDA-approved fat-blocker that reduces dietary fat absorption to support weight loss in adults and teens.
What is the effective dose of Orlistat?
120 mg three times daily (prescription); 60 mg three times daily (OTC)
Is Orlistat safe?
High-dose animal studies showed dose-related liver and kidney damage — monitor liver and kidney function during use
What doesn't Orlistat do?
Not a magic pill — it only blocks fat, not carbs or sugar.
Research Sources
- PubMed
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25