The 30-Second Review

There is no one weight loss pill that will zap away fat. But when combined with healthy food, exercise, and a doctor’s close eye, the best can help you kick-start and maintain an effective weight loss plan. We talked with doctors and combed through over 350 supplements to find the best weight loss pill for sustainable weight control that won't endanger your health or totally waste your money.

Best Overall

Alli is the the only weight loss pill proven effective for eliminating up to 25 percent of the fat you consume, and it's the only pill approved by the FDA. But those benefits come with some gnarly side effects like stomach pain, nausea, diarrhea if you don’t change up your diet.


Twinlab’s Forskohlii Diet Fuel isn’t a proven weight loss aid, but it contains several ingredients that show some evidence for helping with appetite control, like chromium, magnesium, and green tea leaf extract. Bonus: Unlike most supplements on the market, it doesn’t contain any questionable additives.

The Best Weight Loss Pills

The quest for weight loss in America supports a $20 billion industry. For anyone struggling for a healthier way to live, exercise and dieting alone can seem like a long, hard road — and many are looking for a little extra push. That’s often where diet pills come in.

"In almost all cases, additional research is needed to fully understand the safety and/or efficacy of a particular ingredient."

National Institute of Health’s Office of Dietary Supplements

The problem? Where to begin. Over-the-counter weight loss supplements vary widely in terms of ingredients and side effects. They are poorly regulated, and can be dangerous if taken improperly. What’s more, most research conducted on weight loss supplements is dodgy and scientifically inconclusive — the National Institute of Health’s Office of Dietary Supplements states simply “the amount of scientific information available on these ingredients varies considerably … studies supporting a given ingredient’s use are small, of short duration, and/or of poor quality, limiting the strength of the findings. In almost all cases, additional research is needed to fully understand the safety and/or efficacy of a particular ingredient.”

That said, the doctors we we spoke to agreed that, under the right circumstances, supplements can provide a boost to a clean diet and consistent exercise plan. Dr. Donna Ryan, professor emerita of Pennington Biomedical Research Center, cautions that most over-the-counter supplements are bunk, but supports the use of Alli as an effective and safe supplement for weight loss. Its active ingredient, orlistat, is the only weight loss supplement that science considers safe and effective — it works by preventing your body from absorbing up to 25 percent of the fat you ingest from food.

And that right there is your answer: If you’re looking for a guaranteed way to boost your weight loss progress without getting a prescription, plan to shell out at least $33 for 20 days worth of Alli.

But what about the other weight loss supplements lining the aisles of drug stores and spamming your inbox? We were admittedly curious. So, we analyzed the ingredients lists of all the diet pills we could find — over 300 in total. While there’s no evidence to support that they’ll help you lose weight, they at least won’t be harmful to your health.

We like Twinlab Forskohlii Diet Fuel most. It’s a mix of magnesium, chromium, caffeine, medium-chain triglycerides, forskohlii root, and green tea extract, which purports to curb your appetite and aid in digestion. More important to us: There are no junk ingredients and its caffeine is in safe doses.

Group shot of Diet Pills

Our Pick for the Best Weight Loss Pills

Alli Weight Loss Aid CapsulesThe only proven and FDA-approved weight loss pill available over the counter.

Alli emerged is our overall top pick for one very good reason: it is the only FDA-approved over-the-counter weight loss pill out there. Many supplements say they have “FDA-approved ingredients” or are manufactured in “FDA-approved facilities,” but this is just marketing trickery — a way to lend credibility to a product that has no proof backing its claims.

The active ingredient in Alli, orlistat, has been subject to over 100 clinical studies. According to Dr. Ryan, orlistat functions by blocking the enzyme pancreatic lipase. “Pancreatic lipase breaks down ingested fat and allows (fat) to be absorbed,” she says. “Alli blocks the enzyme and fat can’t be absorbed. Alli produces weight loss because you are not absorbing the calories in the fat that passes through your body, and it also helps you stick with a diet that does not have large doses of energy-dense fat.”

Alli claims to prevent your body from absorbing up to 25 percent of the fat you ingest through food, and can boost your weight loss progress up to 50 percent: For every 2 pounds you might lose with just a healthy diet and exercise, Alli claims to help you lose 3 pounds.

Close-up of Alli Diet Pills

The science backs up these bold claims. The Journal of Nutritional Biochemistry found that overweight individuals on orlistat who followed a low-calorie diet “lost and maintained a modest but medically significant amount of weight. The loss was twice as high as that of subjects taking placebo.”

At between $33 and $50 per bottle, Alli is far more expensive than other contenders. Suggested dosages are capped at three pills per day, one per meal with 15 grams of fat — a relief compared to other supplements that require the user to take a whopping nine pills per day. Taking more than three pills per day won’t help you lose weight faster, by the way. A $50 bottle yields just over a month’s worth of supplements.

There’s a big drawback, though: Alli’s main side effect is closely connected to the mechanism that makes it effective.

When your body doesn’t absorb fat, your digestive system eliminates it in uncomfortable and even painful ways. Dr. Ryan notes that Alli is a motivator to stick to a balanced, low-fat diet because if too much fat is ingested, you can experience severe gastrointestinal side effects like stomach pain, nausea, diarrhea, and oily anal leakage. Yikes!

Those unpleasant side effects are intimidating, but they’re also good motivators to develop and maintain a lower-calorie food plan. One more important thing to note: Alli can block your body’s ability to absorb fat-soluble nutrients like vitamins A, D, E, K, and beta-carotene, so Dr. Ryan and the manufacturer recommend you take a multivitamin to compensate.

Did You Know?

Not everyone should take weight loss pills.

Although Dr. Grazia continues to recommend diet and exercise for proper weight management, he suggests that a good candidate for diet pills may be a “healthy overweight person who is less than moderately obese.” According to the CDC, a “healthy overweight person” has a BMI of between 25.0-29.9, and no co-occurring health issues like high blood pressure or high cholesterol. (It’s extra-important to check with your doctor on this: Some ingredients in diet pills — like conjugated lineoleic acid — can interfere with these conditions or medications associated with them.)

Your BMI is a measurement that compares your weight in reference to your height and can be useful, but not definitive, in assessing risks for weight-related illness. Due to concerns about obesity-related illnesses such as diabetes or high blood pressure, Dr. Grazia suggests that individuals who are in the obese territory (a BMI of 30.0 or over) or anyone with health issues should consult a doctor before moving forward with over-the-counter weight loss supplements. You can calculate your BMI on the National Heart, Lung, and Blood Institute's website.

Skipping meals won’t help you lose weight.

Experts warn that eating too little (with or without the aid of diet pills) will slow your metabolism and ultimately increase your body’s tendency to store fat when you return to a normal diet. Also, not eating enough can throw your body into starvation mode, and your body will consume muscle mass. This isn’t just a vanity issue: The more muscle your body has, the more calories it burns naturally. Muscle loss will work against your fat-loss goals!

Neither will appetite suppressants.

The use of appetite suppressants or supplements with stimulants can also have a backslide effect once you stop. While they may cause a short-term boost in energy, when you stop taking them your hunger could roar back something fierce, erasing the gains you made exercising.

Esther Blum joined Dr. Grazia in cautioning against using appetite suppressants. “People who restrict their calories destroy their metabolisms and experience long-term effects of slow metabolisms and increased hunger,” Blum says. “The answer lies in supporting liver function and detoxifying the liver. Diets stop working because the liver becomes congested and is no longer able to metabolize fat from the body, especially if you are adding booze and sugar and junky chemicals into the mix.”

Diuretics aren’t a long-term solution.

None of the supplements we recommended contained diuretics, which can cause dangerous levels of dehydration. Often marketed as water pills, diuretics like PharmaFreak RIPPED or GNC TotalLean Waterex capsules work via false promise: By forcing your body to expel water, they make you feel thinner very quickly. But the loss of water can’t last, and as soon as you stop taking them, your body will gain water weight back fast.

Always tell your doctor if you are taking other medications.

The FDA says simply: “Mixing medications and dietary supplements can endanger your health.” Even small amounts of excess vitamins, stimulants, or minerals can change the way prescription medications are absorbed into your bloodstream, making them more or less potent and potentially causing physical side effects.

Here's how to get the most out of your weight loss pills

  • Enjoy moderate food intake. To paraphrase and expand on Michael Pollan’s famous rules: Eat food, not too little, not too much, mostly plants. Choose a diet plan that fits your personality, lifestyle, and eating preferences, and consult with your doctor or a nutritionist for specifics.
  • Get regular exercise. Studies show that any increase in physical activity can help you shed pounds, particularly if you have a sedentary job. Building muscle mass will help you keep the fat off and raise your metabolism.
  • Drink plenty of decaffeinated fluids. Proper hydration will aid in exercise and overall physical performance while maintaining metabolism.
  • Get on a regular sleep schedule. Poor sleep can lead to weight gain, erode healthy exercise habits, and lead to bad food decisions.
  • Be realistic. Set realistic, attainable goals for weight loss. Aim for losing 5 percent of your body weight and see how you feel. Plan to lose no more than 1-2 pounds a week by burning 500-1,000 more calories per day than you consume. That’s a sustainable level that makes it easier to not fall off the wagon or get discouraged.

The Best Weight Loss Pills: Summed Up

Weight Loss Pills The Best
Alli Weight Loss Aid Capsules
Twinlab Forskohlii Diet Fuel
Safe Runner-Up