GLP-1 Drugs vs Weight-Loss Supplements: What the Trials Show
In large trials, semaglutide and tirzepatide helped people lose about 15% to 21% of their body weight over 68 to 72 weeks. The best-studied weight-loss supplements manage about 0 to 2 kg. The drugs have real side effects and the weight returns if you stop. Compounded copies are not FDA-approved.
By Sift Nutrition Editorial TeamHow we review
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GLP-1 drugs are in a different league from weight-loss supplements. In large, placebo-controlled trials, weekly semaglutide (Wegovy) helped adults with obesity lose about 15% of their body weight over 68 weeks, and weekly tirzepatide (Zepbound) about 21% on its top dose over 72 weeks. The best-studied supplements, such as green tea extract, glucomannan, garcinia and chromium, averaged somewhere between nothing and 1 kg in their meta-analyses; berberine managed about 2 kg. The drugs come with real trade-offs: nausea and other stomach side effects are common, there are rare serious risks, they cost a lot without insurance, and most of the weight returns within a year of stopping. Compounded copies are not FDA-approved, and the FDA has logged hospitalisations from dosing errors with them.
How GLP-1 drugs work
GLP-1 is a gut hormone released after eating. It tells the brain you are full and slows how fast the stomach empties. Semaglutide copies it and lasts a week in the body. Tirzepatide acts on the GLP-1 receptor and on a second gut hormone receptor, GIP. Both drugs reduce appetite, so people eat less without the constant hunger of ordinary dieting. They are approved for adults with a BMI of 30 or more, or 27 or more with a weight-related condition such as high blood pressure or type 2 diabetes, alongside diet and activity (FDA labels).
What the drug trials found
| Drug and trial | Who and how long | What it found | Evidence grade |
|---|---|---|---|
| Semaglutide 2.4 mg weekly injection (Wegovy), STEP 1, N Engl J Med 2021 (PMID 33567185) | 1,961 adults with overweight or obesity, 68 weeks | 14.9% weight loss vs 2.4% on placebo. 50.5% of people on semaglutide lost 15% or more. 4.5% stopped because of stomach side effects vs 0.8% on placebo | STRONGEST |
| Tirzepatide weekly injection (Zepbound), SURMOUNT-1, N Engl J Med 2022 (PMID 35658024) | 2,539 adults with obesity or overweight, 72 weeks | 15.0%, 19.5% and 20.9% weight loss on 5, 10 and 15 mg vs 3.1% on placebo. 57% on 15 mg lost 20% or more | STRONGEST |
| Tirzepatide vs semaglutide head to head, SURMOUNT-5, N Engl J Med 2025 (PMID 40353578) | 751 adults with obesity, no diabetes, 72 weeks | 20.2% weight loss on tirzepatide vs 13.7% on semaglutide. Side effects were mostly stomach-related in both groups | STRONGEST |
| Oral semaglutide 25 mg daily (Wegovy pill), OASIS 4, N Engl J Med 2025 (PMID 40934115) | 307 adults with overweight or obesity, 64 weeks | 13.6% weight loss vs 2.2% on placebo. Stomach side effects in 74% vs 42% on placebo | STRONGEST |
| Orforglipron 36 mg daily pill, ATTAIN-1, N Engl J Med 2025 (PMID 40960239) | 3,127 adults with obesity, 72 weeks | 11.2% weight loss vs 2.1% on placebo. 5.3% to 10.3% stopped because of side effects vs 2.7% on placebo | STRONGEST |
| Semaglutide and heart outcomes, SELECT, N Engl J Med 2023 (PMID 37952131) | 17,604 adults with heart disease and overweight or obesity, no diabetes, about 40 months | Heart attack, stroke or cardiovascular death in 6.5% vs 8.0% on placebo, a 20% lower risk. 16.6% stopped the drug because of side effects vs 8.2% on placebo | STRONGEST |
These trials were large, double-blind and mostly paid for by the drug makers, Novo Nordisk and Eli Lilly. The results have held up in later trials. Two limits matter. The people in them were motivated volunteers with regular check-ins, so real-world results are often lower. And the averages include people who lost very little.
The weight comes back when you stop
This is the part the marketing skips. In the STEP 1 extension, people who stopped semaglutide after 68 weeks had regained about two-thirds of their lost weight a year later, and their blood pressure and blood sugar gains faded back towards where they started (PMID 35441470). In SURMOUNT-4, everyone took tirzepatide for 36 weeks and lost about 21%; those then switched to placebo regained 14% of their body weight over the next year, while those who stayed on the drug lost a further 5.5% (PMID 38078870). Obesity behaves like a long-term condition, and these drugs treat it for as long as you take them.
Side effects and warnings
- Stomach side effects are common: nausea, diarrhea, vomiting and constipation, mostly while the dose is being increased. In STEP 1 they were usually mild to moderate and eased with time (PMID 33567185).
- Both Wegovy and Zepbound carry a boxed warning because they caused thyroid C-cell tumours in rodents. It is not known whether this happens in people, but they must not be used by anyone with a personal or family history of medullary thyroid cancer or MEN 2 (FDA labels).
- Pancreatitis and gallbladder disease, including gallstones, have occurred. Severe stomach pain that does not go away needs urgent care (FDA labels).
- Low blood sugar is a risk if you also take insulin or a sulfonylurea (FDA labels).
- Not for use in pregnancy. The Zepbound label also advises women on the contraceptive pill to add a barrier method for 4 weeks after starting and after each dose increase (FDA labels).
Compounded semaglutide and tirzepatide: what the FDA says
Many telehealth services sell compounded semaglutide or tirzepatide made by pharmacies, usually for less than the branded drugs. The FDA's position (page current as of 1 Sept 2026) is that compounded drugs are not FDA-approved and should only be used when a patient's medical needs cannot be met by an approved drug. It lists specific concerns: hospitalisations linked to dosing errors, often when patients measure doses out of multi-dose vials; salt forms such as semaglutide sodium and semaglutide acetate, which are different active ingredients from the approved drugs; products labelled as coming from pharmacies that did not make them; and vials arriving warm. A poison-centre case series described three people who got sick after dosing mix-ups with compounded semaglutide, two of them from 10-fold overdoses (PMID 37392810).
The FDA also lists red flags for telehealth sellers: claims that a compounded drug is 'the same as' an approved drug, prices that seem too good to be true, no screening and prescription by a licensed clinician, and no clinician to answer questions after the medicine arrives. Oral drops, lozenges and 'GLP-1' supplements sold online have no trials like the ones above.
How weight-loss supplements compare
| Ingredient | Evidence grade | What the trials show | The catch |
|---|---|---|---|
| Green tea extract | WEAK | A Cochrane review found no meaningful effect in six trials outside Japan: 0.04 kg difference from placebo (PMID 23235664). Japanese trials showed 0.2 to 3.5 kg but were too different to pool | Trials lasted about 12 weeks. A separate review found no effect for green tea (Camellia sinensis) alone (PMID 31984610) |
| Glucomannan (konjac fibre) | WEAK | No significant difference from placebo in a meta-analysis of 8 trials: 0.22 kg (PMID 24533610) | Bloating, diarrhea and constipation. Take it with plenty of water |
| Garcinia cambogia (HCA) | WEAK | 0.88 kg more than placebo in a meta-analysis of 9 trials, with uncertain clinical relevance (PMID 21197150). A later review found no effect (PMID 31984610) | Stomach side effects were twice as common as on placebo in one trial |
| Chromium picolinate | WEAK | 0.50 kg more than placebo in a meta-analysis of 11 trials, with high variation between them (PMID 23495911) | Watery stools, dizziness, headaches and hives were reported |
| Berberine | LIMITED | About 2.1 kg more than placebo in a meta-analysis of 12 trials, plus small drops in BMI and waist size (PMID 32690176) | Small, short trials, many in people with metabolic disease. Can interact with other medicines, so check with a pharmacist |
| White kidney bean extract (Phaseolus vulgaris) | WEAK | The only single herb with a statistically significant effect in a large herbal review, but too small to matter clinically (PMID 31984610) | Short trials of mixed quality |
| Multi-ingredient 'fat burners' and 'GLP-1 support' capsules | NONE FOUND | Most have never been tested as sold. Of 315 supplement trials reviewed, only 16 well-run trials showed a real weight difference, of 0.3 to 4.9 kg (PMID 34159755) | Some are spiked with drugs. Of 317 weight-loss supplements the FDA flagged over 10 years, 85% contained sibutramine, a drug withdrawn for heart risks (PMID 30646238) |
Put the numbers side by side. A 100 kg person on the top dose of tirzepatide lost about 21 kg on average in SURMOUNT-1. The same person on garcinia or chromium might lose an extra 0.5 to 1 kg beyond diet alone, and on green tea or glucomannan, probably nothing. No supplement has shown anything close to the drug trials, and none has a heart outcome trial.
Where Java Burn fits
Java Burn is one of the supplements most often mentioned next to GLP-1 drugs. It is now sold as liquid drops: one 1 ml dropper a day, stirred into coffee. The vendor's sales pages name the ingredients but not the amounts. The Supplement Facts panel, as photographed in a September 2026 third-party review, lists a 550 mg proprietary blend of green tea leaf extract, green coffee bean extract, L-carnitine and L-theanine, plus 20 mcg of vitamin D, 1 mg of vitamin B6, 5 mcg of vitamin B12 and 20 mcg of chromium. The label does not say how much of each blend ingredient you get, and we found no published trial of Java Burn itself. So the fairest test is what each ingredient has done in trials.
| Ingredient | Evidence grade | What the trials show | Java Burn's dose |
|---|---|---|---|
| Green tea catechins | WEAK | 1.31 kg more than control across 11 studies of catechins or EGCG with caffeine (PMID 19597519). The effect looked smaller in people who already had over 300 mg of caffeine a day, 0.27 kg against 1.60 kg, though that difference was not statistically significant. The Cochrane review found 0.04 kg in trials outside Japan (PMID 23235664) | Not disclosed, inside the 550 mg blend |
| Green coffee bean extract (chlorogenic acid) | WEAK | 2.47 kg in a meta-analysis of 3 small trials, all at high risk of bias (PMID 20871849). A 2023 meta-analysis of 3 trials with 103 people found 1.30 kg at 500 mg a day or more (PMID 37710316). A widely cited 2012 trial that reported 8 kg in 16 people was retracted in 2014 (PMID 22291473) | Not disclosed, inside the 550 mg blend |
| L-carnitine | LIMITED | 1.21 kg across 37 trials, with the largest effect at about 2,000 mg a day (PMID 32359762). A second meta-analysis of 43 trials found 1.13 kg, mainly in people with overweight or obesity (PMID 31743774) | Not disclosed. The whole blend is about a quarter of 2,000 mg |
| Chromium picolinate | WEAK | 0.50 kg across 11 trials, with uncertain clinical relevance (PMID 23495911) | 20 mcg |
| L-theanine | NONE FOUND | We found no human trials of L-theanine for weight loss. It is studied for calm and focus | Not disclosed, inside the 550 mg blend |
| Vitamins D, B6 and B12 | NONE FOUND | Nutrients, not weight-loss agents. Worth taking only if you are short of them | 20 mcg, 1 mg and 5 mcg |
The dose is the main problem. The blend cannot hold the 2,000 mg of L-carnitine linked to the largest effect, and it could hold 500 mg of green coffee extract only if the other three ingredients shared the last 50 mg. Even at trial doses, these ingredients add up to roughly 1 to 2 kg over a few months in the better studies. Set that against the drug trials: a 100 kg person lost about 15 kg on semaglutide in STEP 1 and about 21 kg on the top dose of tirzepatide in SURMOUNT-1 (PMID 33567185, PMID 35658024). Java Burn costs $49 to $79 a bottle depending on the bundle, far less than a GLP-1 drug without insurance, and it is unlikely to cause the stomach side effects the drugs do. But it is not a cheaper version of the same treatment. If you have obesity or a weight-related condition, the drugs above are the option with real trial results. If you want to try Java Burn anyway, expect a kilogram or so at best, and check with a pharmacist if you take diabetes or other regular medicines.
Getting a GLP-1 drug in the US and UK
- In the US, your own doctor can prescribe Wegovy, the Wegovy pill or Zepbound, and insurance cover varies a lot. Telehealth services also prescribe them and handle prior authorisation. Our review of Measured covers one such service, what it costs and its limits.
- Novo Nordisk and Eli Lilly both sell their drugs directly to self-paying patients in the US, usually for less than the list price. Check those prices before paying a telehealth markup.
- In the UK, the NHS offers Wegovy and Mounjaro (the UK name for tirzepatide) to people who meet its criteria, but access is limited. Many people pay privately through a pharmacy with a UK-registered prescriber. US telehealth services do not serve the UK.
- Whichever route you use, the prescriber should ask about thyroid cancer history, pancreatitis, gallbladder problems, pregnancy plans and diabetes medicines before starting.
Who should skip GLP-1 drugs, or see a doctor first
- Anyone with a personal or family history of medullary thyroid cancer or MEN 2. These drugs are not for you.
- Anyone who is pregnant, breastfeeding or trying to conceive.
- Anyone with a past or current eating disorder. Appetite suppression can make it worse.
- Anyone who has had pancreatitis, or has gallbladder or serious kidney disease.
- Anyone on insulin or a sulfonylurea, whose diabetes doses may need changing.
- Anyone with a BMI under 27, or under 30 without a weight-related condition. The trials did not test cosmetic weight loss.
- Anyone who cannot plan to stay on treatment. Most of the weight returns within a year of stopping.
The bottom line
If you have obesity, semaglutide and tirzepatide are among the most effective non-surgical treatments tested: about 15% to 21% weight loss in large trials, and fewer heart attacks and strokes with semaglutide in people with heart disease. They work only while you take them, stomach side effects are common, and there are rare serious risks. Get the FDA-approved drugs from a prescriber who screens you properly, and treat compounded versions with caution. Weight-loss supplements are not a cheaper version of the same thing. The best of them average 0 to 2 kg, and some contain hidden drugs.
Frequently Asked Questions
How much weight do people lose on semaglutide or tirzepatide?
In the main trials, adults with obesity lost an average of 14.9% of their body weight on weekly semaglutide 2.4 mg over 68 weeks, against 2.4% on placebo (PMID 33567185). On the top dose of tirzepatide they lost 20.9% over 72 weeks, against 3.1% on placebo (PMID 35658024). Everyone in these trials also had diet and activity advice. Averages hide a wide spread: some people lose much more, some very little.
Is tirzepatide better than semaglutide?
In the one head-to-head trial, yes. Among 751 adults with obesity but without diabetes, tirzepatide led to a 20.2% weight loss at 72 weeks against 13.7% with semaglutide (PMID 40353578). Side effects were similar in type, mostly nausea, diarrhea and constipation during dose increases. Cost, insurance cover and how you tolerate each drug matter as much as the average difference.
What happens when you stop a GLP-1 drug?
Most of the weight comes back. One year after stopping semaglutide, people in the STEP 1 extension had regained about two-thirds of the weight they lost, and blood pressure and blood sugar improvements faded too (PMID 35441470). In SURMOUNT-4, people switched from tirzepatide to placebo regained 14% of their body weight over a year, while those who stayed on it kept losing (PMID 38078870). Plan on long-term treatment.
Do any weight-loss supplements actually work?
Not by much. A review of 315 randomised trials of weight-loss supplements and alternative therapies found only 52 were low risk of bias with enough data, and only 16 of those showed a real difference in weight, between 0.3 and 4.9 kg (PMID 34159755). A separate review of herbal medicines concluded there was not enough evidence to recommend any of them (PMID 31984610).
Is compounded semaglutide the same as Wegovy?
No. Compounded semaglutide and tirzepatide are not FDA-approved, which means the FDA has not checked them for safety, effectiveness or quality. The FDA has received reports of hospitalisations linked to dosing errors with compounded injectable semaglutide, often from measuring doses out of multi-dose vials, and warns that salt forms such as semaglutide sodium are different active ingredients from the approved drug. A poison-centre case series described 10-fold overdoses from this kind of measuring mix-up (PMID 37392810).
Does berberine work like a GLP-1 drug?
No. Berberine is sometimes sold as 'nature's Ozempic', but in a meta-analysis of 12 small trials it lowered body weight by about 2 kg on average (PMID 32690176). That is a fraction of the 15% to 21% seen with semaglutide and tirzepatide, and berberine has no large, long trial behind it.
Can Java Burn replace a GLP-1 drug?
No. Java Burn is a coffee add-in with a 550 mg blend of green tea, green coffee, L-carnitine and L-theanine, and it has no published trial of its own. In meta-analyses those ingredients added roughly 1 to 2 kg of weight loss at their trial doses, for example 1.31 kg for green tea catechins (PMID 19597519) and 1.21 kg for L-carnitine (PMID 32359762). Semaglutide and tirzepatide led to about 15% to 21% weight loss in their main trials.
How we reviewed this article
Our editorial team researches each product using the manufacturer's published ingredient list, publicly available studies on the key ingredients, pricing and guarantee terms, and verified customer feedback. Ratings reflect transparency, value, and evidence. Never commission.
Content is reviewed and updated regularly. Last reviewed: 2026.
Medical disclaimer: This content is for informational purposes only and is not medical advice. Supplements are not intended to diagnose, treat, cure, or prevent any disease. Individual results vary. Consult a qualified healthcare professional before starting any supplement, especially if you are pregnant, nursing, taking medication, or have a medical condition.