Do Fat-Burning Pills Work?

Given that nearly three-quarters of American adults are overweight or obese, it's no wonder that products claiming to help you burn fat have proliferated widely. However, there's little evidence that such products work.

In fact, the term "fat-burning pills is a misnomer," says Dr. Matthew Apel, a bariatric surgeon with Blossom Bariatrics in Las Vegas. "There aren't any medications that directly target fat cells."

However, there are some other products out there that can support weight loss efforts, including:

-- Pills to increase your metabolism, which may slightly increase how many calories you burn.

-- Pills to decrease appetite, which can help you decrease calories consumed.

-- Pills that reduce fat absorption in the GI tract, which can limit the number of calories absorbed.

Over-the-counter products marketed for weight loss often contain one or more of the following ingredients that are intended to help you shed more weight faster:

-- Caffeine.

-- Yohimbine.

-- Green tea extract.

Caffeine

Caffeine is that familiar pick-me-up that's found in a variety of food and drinks, including coffee, tea, colas and chocolate. It's also often used in pills marketed for weight loss because it has metabolism-boosting effects.

Though it's fairly ubiquitous, caffeine is considered a drug because it stimulates the nervous system. It can also be dangerous in large quantities and cause a range of uncomfortable effects, including anxiety, racing heart, jitters and insomnia.

The U.S. Food and Drug Administration notes that rapid consumption of high levels of caffeine -- on the order of 1,200 milligrams per day -- could lead to seizures. Lisa Cooper, a registered dietitian with Orlando Health in Florida notes that if you consume 10 grams (or 10,000 milligrams) of caffeine -- equivalent to what would be found in about 100 cups of coffee -- that amount of caffeine can be fatal. A typical 8-ounce cup of drip-brewed coffee contains about 100 milligrams of caffeine. "These toxic levels are usually achieved with caffeine powders or pills." And these products may be labeled as supporting weight loss, so handle with care.

[READ: Probiotics for Weight Loss.]

Yohimbine

Yohimbine, also known as quebrachine, is a compound derived from the bark of an evergreen tree that's native to west and central Africa. It's used in veterinary medicine to reverse sedation in dogs and deer. It's also long been used as an aphrodisiac and forms the primary ingredient of a prescription medication called yohimbine hydrochloride, an erectile dysfunction medication.

Yohimbine has been suggested as an antidote to a variety of human problems, ranging from the sexual dysfunction that's often a side effect of antidepressant medications to treating anxiety and low blood pressure. Most of these assertions, including claims that it can help you lose weight, have little scientific evidence backing them.

It's also important to note that yohimbine can also cause some potentially serious side effects, including nausea, high blood pressure, racing heartbeat and anxiety. Taking high doses can induce difficulty breathing and potentially even death.

A 2013 case study in the Journal of Analytical Toxicology described two cases of acute yohimbine intoxication, where the deceased had high concentrations of the compound in the blood. The study noted that "an average oral dose of 5 to 15 milligrams produces a therapeutic whole blood level range of 40 to 400 ng/mL (nanograms per milliliter)" but "overdoses leading to neurotoxic effect have been seen with blood concentrations up to 5,000 ng/mL."

A dose of just 40 mg per day could be too much, and you may be getting more than you bargain for. A 2015 study in the journal Drug Testing and Analysis analyzed 49 brands of supplements that contain yohimbe or yohimbine and found that 39% of the samples contained pharmaceutical grade extract of the compound. Only two samples out of the 49 "provided consumers with both accurate information about the quantity of yohimbine as well as information about yohimbine's known adverse effects," the study noted.

[SEE: The Best Exercises to Build Muscle and Lose Weight at the Same Time.]

Green Tea Extract

Green tea extract is widely promoted as a natural energy booster and can be found in many energy shots and drink products. It's made from dried green tea leaves and contains caffeine and plant compounds called catechins, a type of antioxidant that can protect against cellular damage.

A typical cup of brewed green tea contains 50 to 100 milligrams of catechins and 30 to 40 milligrams of caffeine.

There's some evidence that consuming green tea or green tea extract that contains 150 to 2,500 milligrams of catechins each day is associated with improved cholesterol profiles, which could mean less risk of coronary artery disease.

Epigallocatechins-3-gallate (EGCG) is the most abundant catechin in tea and may reduce inflammation, protect the heart and brain and potentially aid weight loss. Green tea is a rich source of it, but other types of tea and fruit and nuts also provide EGCG.

If you're reaching for a drink to add more green tea to your diet, check the label. Many products contain high levels of sugar or other sweeteners and added caffeine. Instead, brew fresh green tea at home to save a lot of calories and reduce the risk of potentially dangerous side effects. Drinking between two and four cups of green tea per day is generally considered safe.

[READ: Does Detox Tea Help With Weight Loss?]

A Temporary Fix

With any product you use, you may see some results, but "only when also incorporating healthy diet and exercise and only temporarily while you're on them," Apel says. "Unfortunately, once stopped, the weight tends to return."

What's worse, they may not be safe, he adds. "They're not safer than not using them at all. They have a myriad of side effects and potential deleterious effects on one's health. They can also be habit forming," so on balance, he says "the risk/benefit ratio is not in favor of their use."

Prescription Medications for Weight Loss

While using a supplement to help you lose weight might not be the best idea, there are a few prescription medications for weight loss on the market that your doctor could prescribe if your situation warrants it. Your doctor might recommend trying one of the following medications in combination with increased exercise and improved diet.

-- Saxenda (liraglutide) is an injected medication used for chronic weight management.

-- Contrave (naltrexone HCI/bupropion HCI) is a combination of two medications in one tablet that helps control feelings of hunger and cravings.

-- Orlistat is available both as a prescription -- sold as Xenical, a 120 mg pill -- and over-the-counter medication -- sold as Alli, a 60 mg pill. This lipase inhibitor prevents some fat in foods from being absorbed in the intestines.

-- Phentermine, sold under brand names Adipex-P, Ionamin and Pro-Fast, is a prescription appetite suppressant taken as an oral capsule or tablet.

-- Qsymia, a combination medication that contains phentermine and topiramate, is a once-daily appetite suppressant pill.

"All have different actions and serve to reduce appetite and/or increase metabolism, but none burn fat per se," Apel says. They all also have potential side effects, with some being quite severe.

"If you're looking for long-term weight loss, there are no good medications currently available. And if you're morbidly obese, they definitely won't do the trick to lose a meaningful amount of weight," Apel says. However, some medications can help support weight loss after bariatric surgery and may be useful in certain contexts and on the advice of a physician.

Exercise and Diet Are Critical

Instead of reaching for a pill or powder, the best way to shed excess weight is through increasing physical activity and watching your diet. To lose a pound of body weight, you need to create a calorie deficit of 3,500 calories. One way to do that is by increasing how many calories you burn each day by adding exercise.

Janet Lee, a doctor of Chinese medicine, yoga instructor and health journalist based in Kansas City, Missouri, says a mix of strength training, cardio and high intensity interval training is generally best for supporting your weight loss efforts. "I don't know that we know what the perfect formula is," but in general, aiming to include high intensity interval training two or three times a week," and then if you're doing daily workouts, have another two to three days of moderate intensity cardio exercise."

You should also be seeking to include two or three strength workouts a week. "You can mix those with your cardiovascular exercise and you can make that really intense, or you could make it more moderate intensity," Lee says.

As far as diet goes, there are an endless number of ways to alter your eating habits to reduce caloric intake. U.S. News & World Report's annual ranking of best diets for weight loss lists the flexitarian diet and WW (formerly Weight Watchers) in a tie for the best way to lose weight sustainably.

Increasing your intake of protein and fiber may also help you feel fuller longer and may help you reduce your overall caloric intake. Protein can help stimulate the metabolism. However, simply adding a protein powder could do more harm than good, as these products still contain calories and may contain added sugar that could contribute to weight gain.

Lee says that while you're trying to create a calorie deficit, restricting yourself too much can end up backfiring. "I don't believe in restrictive diets. They work in the short term and can give you results. But then in the long term, you're just going to gain the weight back when you start eating normally."

Instead, she recommends opting for a plant-based diets such as the Mediterranean diet because of its heart health and anti-inflammatory benefits. And, "just try to limit your portions and limit your calories. It's calories in, calories out, for the most part. I know people can always argue that point, but for the most part, it's calories in verses calories out."

Save the money you would spend on a pill or supplement to pay for a gym class or higher quality, fresh produce.