No single over-the-counter appetite suppressant works dramatically for everyone, but a few options have meaningful evidence behind them. The only FDA-approved OTC weight loss product is Alli (orlistat), which works by blocking fat absorption rather than suppressing appetite directly. Everything else on store shelves is sold as a dietary supplement, meaning it hasn’t been evaluated by the FDA for effectiveness. That distinction matters when you’re comparing products.
The Only FDA-Approved OTC Option
Alli is a 60-milligram version of the prescription drug orlistat, approved for adults 18 and older with a BMI of 25 or more. It works by preventing your intestines from absorbing about 25% of the fat you eat. That unabsorbed fat passes through your system, which is why the most common side effects involve oily or loose stools, especially after high-fat meals.
Alli doesn’t suppress appetite in the traditional sense. You won’t feel less hungry. Instead, it reduces how many calories your body actually takes in from fat. Many people find the digestive side effects unpleasant enough that they naturally start choosing lower-fat foods, which indirectly reduces calorie intake. It’s effective but modest, and it works best alongside a reduced-calorie diet.
Glucomannan: The Fiber Approach
Glucomannan is a soluble fiber extracted from the root of the konjac plant. It absorbs water and expands in your stomach, creating a physical sense of fullness. Clinical trials have used doses around 4 grams per day, split across three doses taken with a full glass of water about 30 to 60 minutes before meals. The upper practical limit for soluble fiber supplements is generally considered to be 10 grams per day.
The appetite-suppressing effect is real but not dramatic. You feel moderately fuller before meals, which can help you eat smaller portions without relying on willpower alone. The main side effects are bloating, gas, and mild digestive discomfort, particularly when you first start taking it. Starting with a lower dose and increasing gradually helps. Glucomannan can also slow the absorption of oral medications, so spacing it at least an hour away from any pills you take is important.
If you’re looking at fiber supplements more broadly, taking them in the morning before breakfast may help regulate appetite throughout the day and reduce late-night cravings.
5-HTP: Targeting Cravings Through Serotonin
5-HTP is a compound your body naturally produces as a building block for serotonin, the brain chemical involved in mood and satiety. When serotonin levels are higher, the brain tends to signal fullness sooner and reduce cravings for carbohydrates and sugary foods specifically.
In studies of obese women, 5-HTP supplementation over five weeks led to earlier feelings of fullness during meals, reduced food intake, and weight loss. Separate research found that people taking 5-HTP showed a significant reduction in carbohydrate consumption in particular. The theory is straightforward: when serotonin is abundant, your brain stops sending urgent signals for quick-energy foods like bread, sweets, and pasta.
The catch is that 5-HTP interacts with several common medications, particularly antidepressants that also raise serotonin levels. Combining them can push serotonin dangerously high. Side effects on its own can include nausea, digestive upset, and drowsiness. It’s one of the more effective supplements for curbing carb-heavy overeating, but it requires more caution than a fiber supplement.
Green Tea Extract: Mild but Well-Studied
Green tea extract contains compounds called catechins that may influence appetite through two pathways. First, they can slow the breakdown of norepinephrine, a brain chemical that increases alertness and slightly suppresses hunger. Keeping norepinephrine active longer also boosts your metabolic rate and fat burning. Second, some research suggests the primary catechin in green tea (EGCG) can modestly delay gastric emptying, meaning food stays in your stomach longer and you feel satisfied for a more extended period.
The effects are subtle. You’re not going to skip meals because you took green tea extract. But combined with caffeine (which green tea naturally contains), it provides a mild reduction in appetite along with a small metabolic boost. It’s one of the safer options, though concentrated extracts taken on an empty stomach have been linked to liver stress in rare cases. Taking it with food reduces that risk.
Berberine: Popular but Overhyped
Berberine, a compound found in several plants, has gained enormous popularity on social media as “nature’s Ozempic” for its supposed ability to mimic GLP-1 drugs. A 2025 randomized clinical trial published in JAMA Network Open put this claim to the test: 337 participants with obesity took either berberine (1 gram daily) or a placebo for six months. The result was that berberine showed no significant effect on visceral fat or liver fat compared to placebo. Its safety profile was excellent, but its weight loss benefits did not materialize in this rigorous trial.
Berberine does have legitimate uses for blood sugar regulation, and earlier, smaller studies hinted at metabolic benefits. But the evidence does not support using it as an appetite suppressant or a stand-in for prescription weight loss medications.
Why Tolerance Matters
One issue that applies to nearly all appetite suppressants, whether prescription or over-the-counter, is tolerance. Supplements that reduce hunger effectively as a single dose or over a few weeks often lose their effectiveness with chronic use. The brain adapts: receptors that mediate the appetite-suppressing signal get downregulated, and the body’s hunger control systems recalibrate around the new input.
This is particularly relevant because weight management is a long-term process. A supplement that works well for the first month but stops working by month three isn’t going to deliver lasting results on its own. Some people cycle supplements (using them for several weeks, then taking a break) to try to maintain effectiveness, though this strategy hasn’t been well studied. The practical takeaway is that no OTC suppressant replaces the need for sustainable changes in how and what you eat.
Comparing Your Options
- Alli (orlistat): The only FDA-approved OTC option. Blocks fat absorption rather than suppressing appetite. Effective but causes digestive side effects with fatty meals.
- Glucomannan: Soluble fiber that physically fills your stomach. Modest appetite reduction, very safe, best taken 30 to 60 minutes before meals with plenty of water.
- 5-HTP: Raises serotonin to promote earlier fullness and reduce carb cravings. More potent than fiber but carries interaction risks with antidepressants and other serotonin-affecting medications.
- Green tea extract: Mildly suppresses appetite and slightly boosts metabolism. The most subtle effect of the group but also among the safest for most people.
- Berberine: Despite social media claims, a large clinical trial found no significant fat reduction. Not supported as an appetite suppressant.
If you want the most evidence-backed, lowest-risk starting point, glucomannan or a similar soluble fiber supplement is the safest bet. If carbohydrate cravings are your primary challenge, 5-HTP has stronger targeted evidence. And if you want the only product that’s actually gone through FDA approval for weight loss, Alli is it, though its mechanism is fat blocking rather than hunger reduction. None of these will produce results comparable to prescription medications, but paired with dietary changes, they can provide a meaningful edge.