Treatments and supplements · Orlistat (Alli, Xenical)

Does orlistat really help you lose weight and what are the side effects?

What we can tell you today: how thoroughly this has been studied.

Thoroughly studied

17 studies, of which 11 bring together the results of several trials in people. This is as strong as evidence gets.

5 Repeated evidence 11 studies

4 Large controlled trial 6 studies

This says how thoroughly something has been studied — not whether it works for you. What each study actually found is in the study itself, and in the plain-language write-ups we are adding.

Appears under: Weight loss and GLP-1

The studies

5 Repeated evidence Effect of orlistat on plasma lipids and body weight: A systematic review and meta-analysis of 33 randomized controlled trials.
2018 · Pharmacological research · 4,210 participants
5 Repeated evidence Effects of orlistat on blood pressure: a systematic review and meta-analysis of 27 randomized controlled clinical trials.
2019 · Journal of the American Society of Hypertension : JASH · 8,150 participants
5 Repeated evidence Reporting of harms outcomes: a comparison of journal publications with unpublished clinical study reports of orlistat trials.
2017 · Trials
5 Repeated evidence Improvement of plasma adiponectin, leptin and C-reactive protein concentrations by orlistat: a systematic review and meta-analysis.
2017 · British journal of clinical pharmacology
4 Large controlled trial Treatment of obesity and metabolic-associated fatty liver disease with a diet or orlistat: A randomized controlled trial.
2023 · The American journal of clinical nutrition · 118 participants
5 Repeated evidence Long-Term Effects of Orlistat on Lipid Metabolism and Anthropometric Indices: A Meta-Analysis of Clinical Trials.
2026 · Journal of obesity · 1,369 participants
5 Repeated evidence Discontinuation due to adverse events in randomized trials of orlistat, sibutramine and rimonabant: a meta-analysis.
2009 · Obesity reviews : an official journal of the Internatio
5 Repeated evidence Effect of orlistat-induced weight loss on blood pressure and heart rate in obese patients with hypertension.
2003 · Journal of hypertension · 628 participants
5 Repeated evidence A systematic review of the clinical effectiveness of orlistat used for the management of obesity.
2004 · Obesity reviews : an official journal of the Internatio
5 Repeated evidence An integrated analysis of liver safety data from orlistat clinical trials.
2013 · Obesity facts · 30,000 participants
5 Repeated evidence Orlistat and sibutramine beyond weight loss.
2008 · Nutrition, metabolism, and cardiovascular diseases : NM
5 Repeated evidence Orlistat in responding obese type 2 diabetic patients: meta-analysis findings and cost-effectiveness as rationales for reimbursement in Sweden and Switzerland.
2005 · International journal of obesity (2005) · 1,249 participants
4 Large controlled trial Weight control and risk factor reduction in obese subjects treated for 2 years with orlistat: a randomized controlled trial.
1999 · JAMA · 1,187 participants
4 Large controlled trial Effect of Orlistat on Live Birth Rate in Overweight or Obese Women Undergoing IVF-ET: A Randomized Clinical Trial.
2021 · The Journal of clinical endocrinology and metabolism · 439 participants
4 Large controlled trial Effect of orlistat on weight regain and cardiovascular risk factors following a very-low-energy diet in abdominally obese patients: a 3-year randomized, placebo-controlled study.
2007 · Diabetes care · 383 participants
4 Large controlled trial Efficacy and Safety of Lipase Inhibitor Orlistat in Japanese with Excessive Visceral Fat Accumulation: 24-Week, Double-Blind, Randomized, Placebo-Controlled Study.
2020 · Advances in therapy · 100 participants · manufacturer helped fund this
4 Large controlled trial Orlistat, a lipase inhibitor, for weight maintenance after conventional dieting: a 1-y study.
1999 · The American journal of clinical nutrition · 729 participants