Appetite suppressants are types of supplements that work by reducing appetite, thereby decreasing food consumption and promoting weight loss.
While certain types of appetite suppressants can only be prescribed by a doctor, many are available over the counter.
Here’s a review of 12 over-the-counter appetite suppressants, their effectiveness and safety.
Conjugated Linoleic Acid (CLA) is a type of polyunsaturated fatty acid naturally found in foods like dairy and beef. It’s also sold in concentrated form as a weight loss supplement.
How it works: CLA has been shown to affect appetite-regulating genes and hormones. It may also boost the number of calories burned at rest, increase lean body mass and stimulate fat loss (1).
Effectiveness: While CLA reduces appetite and intake in animal studies, it has not been shown to reduce appetite in humans (2).
A 12-week study in 62 people demonstrated that 3.9 grams of CLA per day had no effect on appetite, body composition or the number of calories burned (3).
Though CLA supplements have been shown to promote fat loss in some studies, its impact on weight loss is small.
For example, a review of 15 studies found that overweight individuals who supplemented with CLA for at least six months only lost an average of 1.5 pounds (0.7 kg) more than people in the control group (4).
Side effects: Taking CLA may result in unpleasant side effects, such as diarrhea and gas. Supplementing long term may even cause serious complications, such as liver damage and increased inflammation (5, 6)
Summary CLA is a dietary supplement branded as an appetite reducer. However, human studies have shown that CLA has little impact on appetite and weight loss.
Synephrine is structurally similar to the once-popular weight loss drug ephedrine, which has been banned from use in dietary supplements since 2004 due to serious side effects (7).
Bitter orange supplements are marketed to promote weight loss by reducing appetite and are available over the counter.
How it works: Bitter orange is believed to encourage weight loss by increasing your basal metabolic rate — or calories burned at rest — therein stimulating fat breakdown and suppressing appetite (8).
Effectiveness: Though research has shown that synephrine increases the numbers of calories burned, its effect on weight loss is inconclusive (9).
Because bitter orange is often combined with other compounds — such as caffeine — in weight loss supplements, it’s difficult to interpret its effectiveness.
A review of 23 studies found that 20–35 mg of synephrine per day increased metabolic rate and had a modest impact on weight loss.
However, some of the studies resulted in no weight loss or even weight gain after treatment with synephrine (10).
Side effects: Reported side effects of synephrine include increased heart rate, elevated blood pressure and anxiety.
However, it’s not yet understood whether synephrine alone or combined with other stimulants causes these symptoms (11).
Summary Bitter orange contains a compound called synephrine that may boost metabolism and encourage weight loss. However, research shows mixed results.
Made with an extract derived from the peel of the Garcinia gummi-gutta fruit, garcinia cambogia pills are used to suppress appetite and promote weight loss.
How it works: Garcinia cambogia extract contains hydroxycitric acid (HCA), which may reduce appetite by increasing serotonin levels in your brain and reducing the metabolism of carbohydrates (12).
Effectiveness: A review of 12 studies found that participants who supplemented with garcinia cambogia containing 1,000–2,800 mg of HCA per day for 2–12 weeks lost an average of 1.94 pounds (0.88 kg) more than those who consumed placebo pills (13).
Another study in 28 people demonstrated that garcinia cambogia was more effective at reducing appetite, increasing fullness and decreasing hunger than a placebo (14).
However, other studies have shown that garcinia cambogia has little to no effect on appetite or weight loss (15).
Side effects: Though generally considered safe, consuming garcinia cambogia may lead to side effects in some people, such as headaches, diarrhea, nausea, irritability and even liver failure in extreme cases (16).