Elephant yams contain a type of fiber that is common in dietary supplements for weight loss.
Elephant yams contain a type of dietary fiber called glucomannan which is common among dietary supplements.anoopkrishnan / Getty Images
  • Common weight loss supplements like green tea extract and caffeine may help you lose some weight.
  • Most dietary supplements work by curbing appetite, boosting metabolism, or facilitatating fat burn.
  • But adding a supplement to your diet will not help you lose as much weight as eating healthy.
  • Visit Insider's Health Reference library for more advice.

These days, you may find yourself inundated with advertisements for products that promise to help you lose weight

These weight loss supplements often contain plant-based extracts that are purported to help control your appetite, boost your metabolism, or facilitate fat burning. And they're extremely popular.

The global market for weight loss products and services hit $254.9 billion in 2021, and it's estimated to reach $377.3 billion by 2026. 

With an ever-increasing variety of weight loss supplements out there, it's next to impossible to research them all to evaluate the pros and cons and determine which — if any — might work for you. 

Here's what experts and current research say about some of the most popular weight loss supplements, and whether or not they're actually effective.

Do weight loss supplements work?

Before we get into the details, there are a few things you should know about dietary supplements (not to be confused with FDA-approved prescription pills proven to aid weight loss.) 

While these "quick fixes" may be tempting, Zuma Nutrition registered dietitian Nick Sopczak says most don't lead to substantial weight loss, especially without making other lifestyle changes, like improving your diet and increasing physical activity. 

A 2021 review of dietary supplements found that out of over 300 studies only 16 had sufficient evidence for significant weight loss. The vast majority of the studies' results were unreliable due to factors like bias and duration, the researchers reported. 

The review also noted that dietary supplements are not regulated by the FDA as strictly as many other prescription and over-the-counter drugs, meaning those products can be marketed without the same level of quality testing to demonstrate their efficacy. 

According to Sopczak, another issue is that much of the research on these supplements is funded by the weight loss industry, which means results are more likely to highlight the benefits while downplaying any negative aspects.

Many popular supplements are not only ineffective, but have harmful side effects, like constipation, diarrhea, elevated heart rate, or kidney problems, says Sopczak.

With that, here's a list of 11 common dietary supplements.

1. Caffeine

How it works: Research suggests that caffeine may support weight loss by suppressing appetite and increasing calorie burning, says Rekha Kumar, MD, an endocrinologist at Weill Cornell Medicine and medical director of the American Board of Obesity Medicine.

What the research says: A small 2012 study found that overweight and obese participants who drank 200 milliliters of coffee along with breakfast consumed fewer calories at the following meal and throughout the day compared to those who drank water. This effect was even more dramatic in the group who drank coffee with a higher amount of caffeine. 

Overall effectiveness: While caffeine alone won't likely make you lose weight, it may be an effective addition to your overall weight loss plan, says Sopczak. 

Side effects: If you are sensitive to caffeine and consume too much, you may experience side effects like restlessness, insomnia, jitters, and anxiety.

2. Green coffee extract

How it works: Green coffee extract comes from coffee beans that haven't been roasted yet — and these unroasted beans contain natural antioxidants known as chlorogenic acids that are believed to reduce the amount of glucose, aka sugar, you absorb after a meal. Excess glucose is what your body stores as fat, so absorbing less may help with weight loss by preventing fat storage.

What the research says: A 2011 review of three studies found that overweight or obese adults who took a green coffee extract supplement alongside their normal diet lost about 5.4 pounds, on average, compared to those who took a placebo. More research is needed, researchers said, since studies had very small sample sizes, short durations, and a strong risk of bias.

Overall effectiveness: Larger, more well-designed studies are needed to determine whether or not green coffee extract is actually effective, says Sopczak — but the NIH reports it may help you lose a small amount of weight.

Side effects: While green coffee beans have less caffeine than roasted coffee beans, you may still experience caffeine-related side effects, says Sopczak — like irritability, anxiety, jitteriness, headache, insomnia, and irregular heartbeat. To be safe, green coffee extract should be avoided by people who are pregnant or breastfeeding, who have heart disease or high blood pressure, or who are taking anti-anxiety medication.

3. Green tea extract

How it works: Green tea extract is high in catechins, a type of antioxidant believed to assist weight loss by increasing the activity of norepinephrine, a hormone that helps burn fat while also making the body more effective at burning calories, says Sopczak. The caffeine in green tea extract may also promote weight loss.

What the research says: Results from studies on green tea extract for weight loss are mixed. According to a 2021 review of 15 studies totaling 499 participants, two studies found green tea extract helped participants burn anywhere from 43.8 to 260.8 extra calories per day. However, it's worth noting these effects were most apparent when participants were also exercising. 

Overall effectiveness: According to the National Center for Complementary and Integrative Health (NCCIH), it has yet to be proven that green tea extracts can produce meaningful, sustainable weight loss. Plus, it's difficult to determine whether green tea extract is effective on its own or if the caffeine in the extract is what's driving studies' results. 

Side effects: Green tea extract is generally well-tolerated, says Sopczak, but may cause symptoms like anxiety, sleeping problems, or irritability in people who are caffeine sensitive or who take large doses — above 400 milligrams per day.

4. Garcinia cambogia extract

How it works: More recent studies suggest that garcinia extract, which comes from a fruit native to Indonesia, can reduce a fat-producing enzyme called citrate lyase and increase levels of serotonin, thus potentially helping to reduce sugar cravings, says Sopczak — but most of these studies have been conducted in animals.

What the research says: A 2013 review of 17 clinical trials totaling 873 subjects found garcinia cambogia had limited to no impact on weight loss. While a separate 2011 review found garcinia cambogia supplementation can lead to a small short-term weight reduction compared with a placebo, all of the studies examined had design weaknesses that likely affected the outcomes, the review's researchers reported.

Overall effectiveness: The NIH has concluded garcinia cambogia has "little to no effect" when it comes to weight loss.

Side effects: Possible side effects associated with this supplement mainly include gastrointestinal symptoms like nausea and diarrhea but in rare cases, it's been linked to liver damage.

5. Glucomannan

How it works: Glucomannan is a type of dietary fiber found in elephant yams. When it absorbs water in your gut, it swells up to 200 times its initial size — and by taking up more room in your stomach, it's thought to help you feel more full so you eat fewer calories, says Sopczak.

What the research says: A 2005 study of 176 overweight, otherwise healthy, subjects found those who took a glucomannan supplement lost more than those who took a placebo — about 8-10 pounds over the course of five weeks. However, other studies have failed to find a connection between glucomannan and weight loss.

Overall effectiveness: According to the NIH, this supplement has little to no effect on weight loss.

Side effects: Glucomannan can cause bloating and gas, says Sopczak, and is not recommended for people with gut or esophageal disorders.

6. Conjugated Linoleic Acid

How it works: Conjugated Linoleic Acid (CLA), a type of fat found in meat and dairy products, may reduce appetite, boost metabolism, and help with fat burning, says Sopczak.

What the research says: A 2007 review of 18 studies found taking CLA was associated with losing 0.2 pounds per week for up to 6 months.

Overall effectiveness: According to the NIH, CLA might help you lose a "very small amount" of weight as well as body fat.

Side effects: CLA can cause some digestive side effects like constipation and diarrhea, and if taken over the long-term, Sopczak says it may increase your risk of fatty liver disease and insulin resistance.

7. Guar gum

How it works: Guar gum, a type of fiber extracted from guar beans, may help you feel fuller longer, thereby reducing how much you eat, says Sopczak.

What the research says: A 2001 review of 20 trials found taking a guar gum supplement resulted in less than 1 pound of weight loss — and that the risk of adverse events like abdominal pain, diarrhea, gas, and cramps outweighed any potential benefits.

Overall effectiveness: The NIH has concluded that taking guar gum "probably doesn't" help you lose weight. Guar gum may help to control appetite, but this same effect could potentially be achieved without unpleasant side effects simply by eating more foods high in soluble fiber such as oats, barley, apples, and oranges.

Side effects: Guar gum may cause gastrointestinal symptoms or trigger an allergic reaction in some people, says Sopczak.

8. Bitter Orange

How it works: Extract from the bitter orange fruit contains synephrine, a compound with stimulant effects believed to reduce appetite and increase fat burning.

What the research says: A 2012 review of 23 studies totaling about 450 participants found nine of the studies showed that synephrine may cause an increase in metabolic rate, suggesting it may be beneficial in weight management. However, researchers said well-controlled, longer-term studies involving only bitter orange extract are needed since about two-thirds of subjects also consumed caffeine, which may have impacted results.

Overall effectiveness: While bitter orange extract may slightly suppress appetite and increase how many calories you burn, the NIH says the word is still out on whether it can actually help you lose weight.

Side effects: The chemical composition of synephrine is similar to ephedra, which has been banned from dietary supplements by the US Food & Drug Administration (FDA). Research on the potentially harmful effects of bitter orange is inconclusive — some studies found bitter orange raised heart rate and blood pressure, while others found it didn't have cardiovascular effects at common doses (up to 100 milligrams).

9. *Ephedra

How it works: The active ingredient in ephedra, an herb that comes from an evergreen shrub, is a known stimulant that may increase your metabolic rate, thus helping you to burn more calories and ultimately lose weight. 

What the research says: A 2021 review of nine studies totaling 534 overweight or obese participants found products containing ephedrine were associated with around 4.4 pounds of weight loss.

Overall effectiveness: Researchers have struggled to discern the effectiveness of ephedra since there aren't any long-term studies and most studies have also included caffeine, which is known to support weight loss. Ultimately, the risks of these supplements seem to far outweigh the potential benefits.

Side effects: The FDA banned this highly controversial supplement in 2006 because it can increase heart rate and blood pressure, and in rare cases, cause heart attack, stroke, or even death. It's also been linked to nausea, vomiting, and some psychiatric symptoms like anxiety and change in mood — especially in products that also contain caffeine, which can increase the risk of adverse side effects.

10. Chitosan

How it works: Chitosan is a sugar mainly derived from the outer skeletons of crustaceans. According to Sopczak, it is said to turn into a gel-like substance in the stomach which then binds to fat in the intestines, but evidence of this is inconclusive.

What the research says: A 2018 review of 14 trials totaling 1,101 overweight or obese subjects found chitosan supplements slightly reduced body weight — by about 2.23 pounds — in overweight and obese people. 

Overall effectiveness: According to the NIH, chitosan does not bind to nearly enough fat to result in significant weight loss.

Side effects: Chitosan is generally considered safe, but Sopczak says possible side effects include upset stomach, nausea, bloating, and constipation.

11. Chromium

How it works: The mineral chromium is believed to increase lean muscle mass while reducing body fat. It also helps insulin perform properly, which Sopczak says helps the body process carbs, fat, and protein more effectively.

What the research says: A 2013 review of nine trials with a total of 622 participants found overweight and obese adults who took chromium picolinate (a supplemental form of chromium) lost an average of about 2.4 pounds after 12 to 16 weeks. Researchers determined this amount of weight loss was of "debatable clinical relevance" and that more "reliable evidence" is needed to verify the efficacy of these supplements.

Overall effectiveness: The NIH says chromium may help you lose a "very small amount" of body weight and fat. Less than 2.5% of ingested chromium is absorbed in the intestines, which Sopczak says is likely too low to have a significant effect in the body.

Side effects: In supplement form, high doses of chromium can interfere with insulin and other diabetes medications. 

This supplement should also be avoided by those with kidney or liver problems, or with anemia. Kidney damage, worsened depression or anxiety, and irregular heartbeat have been reported in rare cases. 

People with liver or kidney problems, or people with anemia, should not take chromium without first talking to their doctor.

Insider's takeaway

While there's a chance some of these supplements — like green coffee extract, CLA, and chromium — may help support your weight loss efforts, Kumar says there still aren't enough randomized controlled trials to prove they result in significant, sustained weight loss on their own. 

Experts agree none of these products will work miracles without healthy changes to your diet and exercise habits. 

Because of the potential for interactions with medications and side effects, you should always talk to your health care provider before trying any of these supplements.

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