What you can take to lose weight ranges from prescription medications that produce 14% to 20% body weight loss, to over-the-counter options like fiber supplements and fat blockers with more modest effects. The right choice depends on how much weight you need to lose, your health history, and whether you qualify for prescription options. Here’s what actually works, what the evidence shows, and what to realistically expect from each.
Prescription Injections: GLP-1 and GIP Medications
The most effective weight loss medications available today are injectable drugs that mimic gut hormones involved in appetite regulation. These work by targeting areas of the brain that control hunger and food intake, making you feel full sooner and reducing cravings between meals. The FDA has approved three injectable options for long-term weight management.
Semaglutide (sold as Wegovy) is a weekly injection approved for adults and children 12 and older. In clinical trials, people lost an average of 13.7% of their body weight over 72 weeks. Tirzepatide (sold as Zepbound) is also a weekly injection but works on two hunger-related hormones instead of one. In a head-to-head trial published in the New England Journal of Medicine, tirzepatide produced 20.2% body weight loss at 72 weeks compared to semaglutide’s 13.7%. A third option, liraglutide (Saxenda), requires daily injections and is also approved for adults and adolescents 12 and older.
These medications are typically prescribed for adults with a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related health condition like high blood pressure, type 2 diabetes, or high cholesterol. They’re not available over the counter, and they require ongoing use to maintain results. People with a history of pancreatitis, gallbladder disease, or a family history of certain thyroid cancers are generally not good candidates. If you drink heavily or smoke, your provider will likely ask you to address those habits before starting treatment.
Prescription Pills for Weight Loss
If injections aren’t your preference, two oral prescription medications are approved for long-term use. Both are combination drugs that work through different pathways in the brain.
Phentermine-topiramate (Qsymia) combines an appetite suppressant with a drug originally used for seizures and migraines. It’s effective, but comes with notable side effects. Clinical data shows it nearly doubles the risk of anxiety, increases sleep problems by about 55%, and raises the likelihood of irritability more than threefold compared to placebo.
Naltrexone-bupropion (Contrave) pairs an addiction treatment drug with an antidepressant. It reduces appetite and may also reduce food cravings. However, it carries a 72% higher risk of elevated blood pressure, more than triples the risk of dizziness, triples the risk of dry mouth, and increases insomnia by about 50%. It also raises the risk of anxiety by roughly 2.4 times. Previous studies have found that high blood pressure and heart palpitations are among the most common reasons people stop taking it. If you already have blood pressure issues, this one needs careful consideration.
Over-the-Counter: Orlistat (Alli)
The only FDA-approved over-the-counter weight loss drug is a lower-dose version of orlistat, sold as Alli. It works completely differently from the options above. Instead of reducing appetite, it blocks your body from absorbing about 30% of the fat you eat. Undigested fat passes through your system, which means fewer calories are absorbed from meals.
The trade-off is digestive. Oily stools, gas, and urgent bowel movements are common, especially after high-fat meals. Many people find these side effects manageable by keeping dietary fat intake low, which is part of the point. The weight loss is more modest than prescription options, but it doesn’t require a doctor’s visit to start.
Fiber Supplements for Appetite Control
Soluble fiber supplements are one of the more evidence-backed non-prescription approaches. A randomized controlled trial tested a combination of glucomannan, inulin, and psyllium fiber (5 grams taken before each meal, three times daily) over six months. The fiber group lost 7.3% of their body weight compared to 2.4% in the placebo group. Nearly 60% of people taking the fiber achieved at least 5% weight loss, compared to about 27% on placebo.
The mechanism is straightforward: soluble fiber absorbs water and expands in your stomach, making you feel fuller before and after meals. The study measured this directly. Hunger ratings dropped significantly more in the fiber group, while fullness and satiety ratings climbed. Fat mass dropped by 13% more than placebo, and visceral fat (the deep abdominal fat linked to metabolic disease) decreased meaningfully as well.
You can find glucomannan, psyllium, and inulin individually or in combination products at most pharmacies and health food stores. The key is taking them with a full glass of water before meals. Without enough fluid, fiber supplements can cause bloating or, rarely, blockages.
Green Tea Extract and Caffeine
Green tea extract containing catechins (its active plant compounds) increased 24-hour energy expenditure by about 4% in a controlled study published in the American Journal of Clinical Nutrition. It also shifted the body toward burning more fat relative to carbohydrates. Interestingly, caffeine alone at the same dose found in the green tea extract did not produce these effects, suggesting the catechins themselves drive the thermogenic benefit.
A 4% increase in daily calorie burn is real but small. For someone burning 2,000 calories a day, that’s roughly 80 extra calories. It won’t transform your body on its own, but it can contribute as part of a broader strategy. Green tea extract is widely available as a supplement, though high doses have been linked to liver problems in rare cases. Sticking to moderate doses or simply drinking green tea is the safer route.
Berberine: The “Natural Metformin”
Berberine is a plant compound that activates the same cellular energy sensor as the diabetes drug metformin. It stimulates glucose uptake in muscle, liver, and fat tissue, and it promotes the breakdown of stored triglycerides in fat cells. A three-month trial comparing berberine directly to metformin in people with type 2 diabetes found their blood sugar-lowering effects were comparable.
For weight loss specifically, berberine’s effect works through increasing the baseline rate at which fat cells break down stored fat. It also has anti-inflammatory properties in the gut. The weight loss results are modest compared to prescription medications, but berberine is available without a prescription and is generally well tolerated. It can interact with other medications, particularly those processed by the liver, so it’s worth checking for interactions if you take other drugs.
How These Options Compare
The gap between prescription and non-prescription options is significant. Here’s a rough comparison of what to expect over several months:
- Tirzepatide (Zepbound): approximately 20% body weight loss at 72 weeks
- Semaglutide (Wegovy): approximately 14% body weight loss at 72 weeks
- Oral prescriptions (Qsymia, Contrave): typically 5% to 10% body weight loss
- Fiber supplements: approximately 7% body weight loss at 6 months (with lifestyle changes)
- Green tea extract: modest calorie-burning boost of about 4%, supportive rather than primary
- Orlistat (Alli): blocks 30% of dietary fat absorption, typically 3% to 5% additional weight loss
- Berberine: modest weight and metabolic effects, best suited for people with blood sugar concerns
What Actually Matters Alongside Anything You Take
Every clinical trial for every weight loss medication or supplement includes a lifestyle component. The fiber supplement study paired its protocol with a lifestyle intervention. GLP-1 trials include diet and exercise counseling. No pill or injection replaces the fundamentals: eating in a calorie deficit and moving your body regularly. What these tools do is make the deficit easier to sustain, either by reducing how hungry you feel, blocking some calorie absorption, or slightly increasing how many calories you burn.
Protein intake matters more than most people realize during weight loss. When you lose weight, some of that loss comes from muscle, not just fat. Eating adequate protein, roughly 1.2 to 1.6 grams per kilogram of your body weight daily, helps preserve muscle mass. This is especially important if you’re using a GLP-1 medication, where the rapid weight loss can accelerate muscle loss if protein intake is too low. Strength training amplifies this protective effect.