the figures above come from different study designs and different populations — randomised drug trials at the highest approved dose, device trials against a sham, and observational surgical cohorts followed for years in ordinary care. They are shown side by side for orientation, not as a comparison, and no one of them predicts what any one person will lose.
Where everyone starts: food, movement, supplements
Every treatment further down this page is used alongside changes to eating and activity, not instead of them — the trials behind those numbers all included diet and lifestyle support in both arms. Supplements sit apart: they are sold without a prescription and are not regulated as treatments, and the evidence behind each one varies enormously.
These three pages cover that ground in detail, with their own figures and sources.
Older prescription drugs
These are the prescription appetite suppressants that were the standard of care long before the GLP-1 era. They are stimulants, they are controlled substances in the United States, and their labels describe short-term use rather than the open-ended treatment the newer drugs are licensed for. Phentermine has its own page here; the others are grouped together.
In clinical trials, participants lost about 7.5% of their starting body weight.
Health-record cohort, 13,972 people, 24 months — not a trial
Typical cost: $10–$51/mo
Rare genetic obesity
A small number of people have obesity caused by a single identified change in the brain pathway that regulates appetite. One drug is approved specifically for several of those diagnoses, confirmed by genetic testing, and it is not a general obesity treatment. It is on this page so the map is complete.
In clinical trials, participants lost about 23.1% of their starting body weight.
Open-label, single-arm, 10 people, 1 year: the 23.1% figure is the average body-weight change at about one year in an open-label, single-arm trial of 10 people with POMC or PCSK1 deficiency, with no control group, and the 9.7% figure comes from a matching trial of 11 people with leptin-receptor deficiency. Results are reported separately for each condition. The Bardet-Biedl syndrome and acquired hypothalamic obesity figures are reported as change in BMI, not body weight. Figures from these trials cannot be compared with weight-loss drug trials in general obesity.
Price not published
Approved weight-management drugs
These are the drugs approved for long-term weight management, and the part of the field this site covers in the most depth: the weekly and daily injections, the GLP-1 pills, the older combination tablets and a fat blocker. Each has its own page with the trial data, the dosing, the side effects and what it costs.
In clinical trials, participants lost about 20.9% of their starting body weight.
Phase 3, 72 weeks, vs placebo
Typical cost: $299–$449/mo (savings price)
In clinical trials, participants lost about 16.6% of their starting body weight.
Phase 3, 64 weeks, vs placebo
Typical cost: $149–$299/mo
In clinical trials, participants lost about 14.9% of their starting body weight.
Phase 3, 68 weeks, vs placebo
Typical cost: ~$1,350/mo
In clinical trials, participants lost about 12.4% of their starting body weight.
Phase 3, 72 weeks, vs placebo
Typical cost: $149–$349/mo
In clinical trials, participants lost about 9.8% of their starting body weight.
Phase 3, 56 weeks, vs placebo
Typical cost: $30–$400/mo (generic price)
In clinical trials, participants lost about 9.3% of their starting body weight.
Phase 3, 56 weeks, vs placebo + intensive behaviour therapy
Typical cost: $100–$400/mo
In clinical trials, participants lost about 8.5% of their starting body weight.
Phase 3, 1 year (52 weeks), vs placebo
Typical cost: $40–$400/mo (OTC price)
In clinical trials, participants lost about 8% of their starting body weight.
Phase 3, 56 weeks, vs placebo
Typical cost: $1,000–$1,349/mo
Swallowed device
A device is not a drug. This one is a capsule of hydrogel particles that swell with water in the stomach, and it is regulated as a device rather than as a medicine because it works mechanically rather than through the bloodstream.
In clinical trials, participants lost about 6.4% of their starting body weight.
The trial met one co-primary endpoint (the proportion of people losing at least 5% of body weight) but missed the other, a 3% super-superiority margin over the placebo capsules. The FDA review described the benefit as modest and noted that participants at US sites saw a smaller difference than those at European sites.
Price not published
Endoscopic procedures
Endoscopic procedures are done through the mouth with a flexible scope, under sedation, with no incisions and no permanent change to the anatomy. One places a balloon in the stomach for a set period and then removes it; the other stitches the stomach into a narrower tube from the inside.
In the published studies, participants lost about 15% of their starting body weight.
Two randomised trials vs lifestyle, 6–8 months, 543 people
Typical cost: $4,995–$9,000 one-time
In the published studies, participants lost about 13.6% of their starting body weight.
Randomised vs lifestyle, 1 year, 209 people
Typical cost: $9,000–$15,000 one-time
Bariatric surgery
Bariatric surgery permanently changes the stomach, and in a bypass the small intestine as well. It is the most invasive option on this page and also the one with the longest follow-up — people in the surgical cohorts have been tracked for far longer than any medication trial has run. The dedicated guide sets the two kinds of evidence side by side and explains why they are not interchangeable.
In the published studies, participants lost about 29.8% of their starting body weight.
Observational, 44,025 patients, 1 year — not a trial
Price not published
In the published studies, participants lost about 24.4% of their starting body weight.
Observational, 44,025 patients, 1 year — not a trial
Price not published
Common questions
Written and maintained by one person · Built with agentic AI tools · Every number checked against the cited trial · Not medical advice
The studies behind the figures on this page
Each treatment section quotes the headline study recorded against that treatment in this site's data files, and the 14 studies below are those sources. They differ in design, length and population: the drug trials are randomised and placebo-controlled, while the endoscopic and surgical figures come from cohorts followed in ordinary care. Costs are US self-pay or list prices as recorded on the manufacturer and programme pages cited on each treatment's own page, last checked September 2026.
- Lewis 2019 (PORTAL health-record cohort) — Phentermine: 13,972 adults aged 18–64 with a first phentermine prescription between 2010 and 2015 across eight US health systems; 84% were women and mean BMI was 37.8, Up to 3 years of follow-up, with weight measured at 6, 12 and 24 months. Obesity, 2019. View source ↗
- POMC and LEPR phase 3 trials — Setmelanotide: 21 people aged 6 and over with severe obesity due to POMC or PCSK1 deficiency (10) or leptin-receptor deficiency (11), About 1 year. The Lancet Diabetes & Endocrinology, 2020. View source ↗
- SURMOUNT-1 — Tirzepatide: 2,539 adults with obesity or overweight with comorbidities, no type 2 diabetes, 72 weeks. New England Journal of Medicine, 2022. View source ↗
- STEP 1 — Semaglutide (injection): 1,961 adults with obesity or overweight with comorbidities, no type 2 diabetes, 68 weeks. New England Journal of Medicine, 2021. View source ↗
- OASIS 4 — Semaglutide (oral pill): 307 adults with obesity or overweight + at least 1 health condition, 64 weeks. New England Journal of Medicine, 2024. View source ↗
- SCALE Obesity and Prediabetes — Liraglutide: 3,731 adults with obesity or overweight with comorbidities, 56 weeks. New England Journal of Medicine, 2015. View source ↗
- CONQUER — Phentermine / Topiramate: 2,487 adults with obesity and at least 2 weight-related health conditions, 56 weeks. The Lancet, 2011. View source ↗
- COR-BMOD — Naltrexone / Bupropion: Adults with obesity, with intensive behaviour therapy, 56 weeks. Obesity, 2011. View source ↗
- Sjostrom 1-year RCT — Orlistat: 743 adults with obesity, 1 year (52 weeks). International Journal of Obesity, 2000. View source ↗
- ATTAIN-1 — Orforglipron: 3,127 adults with obesity or overweight with comorbidities, no type 2 diabetes, 72 weeks. New England Journal of Medicine, 2025. View source ↗
- GLOW — Plenity (Gelesis100): 436 adults with a BMI of 27-40 and fasting plasma glucose of 90-145 mg/dL, with and without type 2 diabetes, 24 weeks. Obesity, 2019. View source ↗
- Orbera US pivotal trial (IB-005) — Orbera intragastric balloon: 255 adults with a BMI of 30–40 randomised 1:1 to the balloon plus a 12-month behavioural programme or the programme alone, at 15 US sites, 6 months with the balloon in place, 12 months in total. International Journal of Obesity, 2017. View source ↗
- MERIT — Endoscopic sleeve gastroplasty: 209 adults aged 21–65 with class 1 or 2 obesity randomised to the procedure plus lifestyle changes (85 people) or lifestyle changes alone (124 people), 52 weeks, with follow-up to 104 weeks in the procedure group. The Lancet, 2022. View source ↗
- Real-world comparison of GLP-1 drugs and bariatric surgery — Sleeve gastrectomy and gastric bypass: 44,025 US adults with a BMI of 35 or more who started an injectable GLP-1 drug or had bariatric surgery between 2018 and 2024, Up to 3 years. Obesity, 2026. View source ↗
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