The most effective appetite suppressants available today are the newer injectable medications that mimic gut hormones, specifically tirzepatide (Zepbound) and semaglutide (Wegovy). In clinical trials, GLP-1 drugs produce an average body weight loss of roughly 7% to 11%, with tirzepatide generally showing the highest numbers. But “best” depends on your medical history, budget, and whether you qualify for a prescription, so the real answer is more nuanced than a single drug name.
How Appetite Suppressants Work
Prescription appetite suppressants target your brain’s hunger signals through different pathways, and understanding those differences helps explain why some work better than others.
The GLP-1 class, which includes semaglutide (Wegovy) and liraglutide (Saxenda), mimics a hormone your gut naturally releases after eating. This hormone signals the brain to reduce appetite and slows the movement of food out of your stomach, so you feel full longer. Tirzepatide (Zepbound) takes this a step further by mimicking two gut hormones instead of one, which is likely why it tends to produce more weight loss in head-to-head comparisons.
Older stimulant-based options work differently. Phentermine triggers the release of a stress hormone in the brain’s appetite center, raising levels of a satiety signal called leptin. It’s effective at suppressing hunger, but the FDA only approves it for short-term use (a few weeks). A combination pill pairs phentermine with topiramate (Qsymia), which is approved for long-term use and produces more sustained results than phentermine alone.
Naltrexone-bupropion (Contrave) combines two medications originally designed for addiction and depression. Together, they act on reward and craving pathways in the brain. This option tends to produce more modest weight loss than the injectable drugs but works well for people whose overeating is driven more by cravings than by physical hunger.
Comparing Prescription Options
The FDA has approved six medications for long-term weight management. Here’s how they stack up in practice:
- Tirzepatide (Zepbound): Weekly injection. Mimics two gut hormones. Produces the highest average weight loss of any approved medication, often exceeding 15% of body weight in clinical trials. Currently the most potent option.
- Semaglutide (Wegovy): Weekly injection. Mimics one gut hormone. A large Johns Hopkins analysis found GLP-1 drugs in this class produced an average weight loss of about 10.9% in women and 6.8% in men.
- Liraglutide (Saxenda): Daily injection. Same mechanism as semaglutide but requires daily dosing and generally produces less weight loss.
- Phentermine-topiramate (Qsymia): Daily pill. Effective appetite suppression with typical weight loss in the 7% to 10% range. One of the few oral options approved for long-term use.
- Naltrexone-bupropion (Contrave): Daily pill. Targets food cravings and reward-driven eating. Weight loss tends to be more modest, around 5% to 8%.
- Orlistat (Xenical/Alli): Not technically an appetite suppressant. It blocks fat absorption in your gut. Weight loss is generally the lowest of the group, and side effects (oily stools, gas) make it the least popular option. The over-the-counter version, Alli, is available at a lower dose without a prescription.
Side Effects to Expect
GLP-1 drugs (semaglutide, tirzepatide, liraglutide) share a similar side effect profile. Nausea, vomiting, diarrhea, and constipation are by far the most common complaints, especially during the first few weeks as your dose increases. These usually improve with time. Rapid weight loss can also cause visible changes in the face: a hollowed look, sagging around the jaw, and more prominent wrinkles, sometimes called “Ozempic face.”
Less common but more serious risks include inflammation of the pancreas, slowed stomach emptying that doesn’t resolve (gastroparesis), bowel obstruction, and gallstone attacks. If you’re scheduled for surgery requiring general anesthesia, you may need to stop GLP-1 drugs several days beforehand because they slow digestion and your stomach may not be empty when it needs to be.
Stimulant-based options like phentermine carry cardiovascular risks: increased heart rate, elevated blood pressure, and potential for dependence. Naltrexone-bupropion has a rare but real seizure risk, which increases if you drink heavily, have a history of eating disorders like bulimia or anorexia, or are withdrawing from alcohol or sedatives. Bupropion can also stress the liver, and combining it with alcohol raises the chance of serious neurological side effects.
What About Supplements and OTC Options
If you’re looking for something available without a prescription, the evidence is far less impressive. The supplement aisle is crowded with products claiming to suppress appetite, but most lack strong clinical backing.
Glucomannan, a soluble fiber derived from konjac root, is one of the more studied options. It absorbs water and swells to 80 to 100 times its original volume in your stomach, which can create a feeling of fullness. It does improve cholesterol and blood sugar markers in clinical trials. However, a meta-analysis of six randomized trials found no statistically significant difference in body weight between people taking glucomannan and those taking a placebo. In other words, it may help you feel fuller, but that hasn’t reliably translated into measurable weight loss in controlled studies.
5-HTP, a precursor to serotonin, has shown some ability to reduce food intake in small studies at doses of 50 to 200 mg daily. The theory is that boosting serotonin helps regulate appetite and reduce carbohydrate cravings. But the studies are small, mostly older, and not nearly robust enough to compare with prescription options. Green tea extract (EGCG) and similar compounds fall into the same category: plausible mechanism, underwhelming real-world results.
The one OTC exception worth noting is orlistat at the lower Alli dose (60 mg), which is FDA-approved and available at pharmacies without a prescription. It won’t suppress your appetite, but it does block some fat absorption.
Cost and Access
The biggest barrier to the most effective appetite suppressants isn’t a prescription. It’s the price. GLP-1 medications carry list prices around $900 to $1,000 or more per month in the U.S. If your private insurance covers Wegovy, manufacturer coupons can bring the cost down to around $225 for a 28-day supply. Without coverage, coupons still drop the price to roughly $500 per month, which remains steep for an ongoing medication.
Oral options like phentermine-topiramate and naltrexone-bupropion are generally less expensive, and phentermine alone (for short-term use) is available as a low-cost generic. Orlistat’s OTC version, Alli, runs about $40 to $60 per month at most pharmacies.
Insurance coverage varies widely. Many plans still classify weight loss medications as “lifestyle” drugs and exclude them, though this is gradually changing as obesity is increasingly treated as a chronic condition. It’s worth checking your specific plan before assuming coverage.
Weight Regain After Stopping
One critical factor that doesn’t get enough attention: appetite suppressants work while you take them. Studies consistently show that people regain a significant portion of lost weight after discontinuing GLP-1 drugs or other suppressants. These medications don’t reset your body’s weight set point. They override hunger signals for as long as you’re on them. That means the “best” appetite suppressant is one you can sustain, whether that’s through long-term prescription use, pairing medication with lasting dietary changes, or both. Starting a medication with no plan for what happens when you stop is the most common reason people feel these drugs “didn’t work.”