Several supplements have shown the ability to reduce appetite, though none work as dramatically as prescription medications. The most studied options include 5-HTP, glucomannan fiber, green tea extract, berberine, and yerba maté, each working through a different biological mechanism. Some curb cravings by altering brain chemistry, others by physically filling your stomach, and others by changing the hormones that signal fullness. Here’s what the evidence actually supports.
5-HTP: The Serotonin Route
Your brain uses serotonin to regulate feelings of fullness after a meal. 5-HTP is a compound your body naturally produces as a building block for serotonin, and taking it as a supplement raises serotonin levels directly. Higher serotonin translates to feeling satisfied sooner during meals and, notably, reduced cravings for carbohydrates and sugary foods.
The most compelling data comes from a study of obese women who took 5-HTP daily for 35 days. Without making any conscious effort to restrict their eating, participants consumed roughly 500 fewer calories per day than a control group. They reported early satiety, meaning they simply felt full faster. Follow-up research in people with diabetes found similar results: overall energy intake dropped, with about 75% of the reduction coming from carbohydrates and 25% from fats. That pattern makes sense given serotonin’s specific role in dampening carb cravings.
5-HTP is one of the faster-acting appetite supplements. Some people notice changes in hunger within the first week or two, though the full effect may take longer to stabilize. One important caution: because it directly raises serotonin, 5-HTP should not be combined with antidepressants or other medications that affect serotonin levels, as this can lead to a dangerous excess called serotonin syndrome.
Glucomannan: Physical Fullness From Fiber
Glucomannan is a soluble fiber extracted from the root of the konjac plant. It works by absorbing water in your stomach and expanding into a thick gel, which slows digestion and makes you feel physically full. The mechanism is straightforward: a fuller stomach sends stronger satiety signals to your brain, and food moves through your digestive system more slowly, keeping blood sugar steadier between meals.
The clinical reality, however, is more modest than the marketing suggests. In a controlled trial of overweight and moderately obese adults, participants taking glucomannan for eight weeks lost essentially the same amount of weight as those taking a placebo (about 0.4 kg in each group). That doesn’t mean it has zero effect on appetite in the moment, but the measurable weight loss difference was negligible over two months.
There’s also a safety consideration worth knowing. Glucomannan tablets can swell significantly before reaching the stomach, and the Cleveland Clinic notes they’ve been linked to blockages in the throat and intestines. Powder or capsule forms taken with plenty of water are considered safer than tablet forms. If you try glucomannan, take it 30 to 60 minutes before a meal with at least a full glass of water.
Green Tea Extract and EGCG
Green tea extract contains a compound called EGCG that has been shown to reduce food intake in animal studies. EGCG appears to interact with an appetite control pathway that operates independently of leptin, the hormone your fat cells release to signal that you have enough energy stored. That distinction matters because many people with excess weight have become resistant to leptin’s signals, meaning a leptin-independent pathway could still function when leptin-based hunger control has broken down.
The appetite-suppressing effect of green tea extract is milder than what you’ll see with 5-HTP or prescription options. Much of green tea’s reputation for weight management comes from its ability to slightly increase calorie burning rather than dramatically reducing hunger. Think of it as a supplement that nudges multiple dials by a small amount rather than turning one dial sharply. The caffeine content also contributes a mild, short-term appetite reduction that most coffee drinkers will already be familiar with.
Berberine: Hormone-Level Changes
Berberine is a compound found in several plants, including goldenseal and barberry. It affects appetite through a more complex hormonal route than the options above. Berberine increases the release of GLP-1, the same fullness hormone targeted by prescription weight loss drugs. It also raises levels of two other satiety hormones (CCK and PYY) while lowering ghrelin, which is the hormone responsible for making you feel hungry.
Beyond appetite, berberine improves insulin sensitivity, meaning your body handles blood sugar more efficiently. Poor insulin sensitivity is closely tied to hunger spikes and cravings, especially after meals heavy in refined carbohydrates. By stabilizing that cycle, berberine may help reduce the “crash and crave” pattern that drives overeating in many people. Most of the current evidence comes from animal models and mechanistic studies rather than large human weight loss trials, so the real-world effect on your appetite may be less dramatic than the hormonal changes suggest on paper.
Yerba Maté: Slowing Digestion
Yerba maté, a traditional South American tea, suppresses appetite primarily by slowing how quickly food leaves your stomach. In one clinical study, a preparation containing yerba maté increased gastric emptying time from about 38 minutes to 58 minutes compared to placebo. That extra 20 minutes of food sitting in your stomach means prolonged feelings of fullness after eating.
The weight loss results from that study were notable: participants lost 5.1 kg over 45 days compared to just 0.3 kg in the placebo group, and they maintained most of that loss over 12 months. The preparation also contained guarana and damiana, so the effect can’t be attributed to yerba maté alone. Separately, animal studies have found that yerba maté increases GLP-1 and leptin levels, suggesting it promotes satiety through hormonal pathways as well as physical ones.
Yerba maté does contain caffeine, and the main side effects reflect that: restlessness, elevated blood pressure, and difficulty sleeping, particularly if taken later in the day.
How Long Before You Notice a Difference
Most appetite-suppressing supplements take at least a few days to produce noticeable changes, and the full effect often develops over two to four weeks of consistent use. Fiber-based options like glucomannan work almost immediately in terms of physical fullness, but the supplements that alter brain chemistry or hormone levels, like 5-HTP and berberine, need time to build up their effects. If you don’t notice any change in hunger after three to four weeks of regular use at an appropriate dose, that particular supplement likely isn’t going to work for you.
Safety Risks With Unregulated Products
The FDA does not approve dietary supplements before they hit the market, and contamination is a real problem in the weight loss category specifically. FDA laboratory testing has found over-the-counter weight loss products secretly laced with sibutramine (a prescription drug pulled from the U.S. market in 2010 after it was linked to increased risk of heart attack and stroke), amphetamine derivatives, prescription antidepressants, and powerful diuretics that can cause dangerous fluid and electrolyte loss.
These aren’t listed on the label. You’d have no way of knowing they were there without lab analysis. To reduce your risk, choose supplements that carry third-party testing certifications (USP, NSF, or ConsumerLab), and avoid products making extreme claims about rapid weight loss. The supplements with the best safety profiles for appetite suppression, like glucomannan and 5-HTP, are also widely available from established brands that submit to independent testing.
Some herbal ingredients carry their own inherent risks even without contamination. Ephedrine, which was once common in weight loss supplements, can cause seizures, heart attacks, and stroke. Guar gum, another fiber-based option, can swell 10 to 20 times its size and has caused esophageal blockages. Sticking with well-researched options at standard doses, rather than exotic blends promising dramatic results, is the safer path.