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Vitamins and Supplements for Weight Loss

What vitamins and supplements can help with weight loss? Here’s the science behind 7 of the most popular weight loss supplements


spinner image What you need to know about vitamins, supplements and weight loss.
Sarah Rogers; (Source: Getty Images (2))
Sarah Rogers (Getty: X)

If you want to lose weight, you already know what you’re supposed to do: eat healthier and move more. But as anyone who has ever tried to slim down knows, shedding those extra pounds is a lot harder than it sounds – especially over age 50.

Unfortunately, no over-the-counter weight loss vitamin or supplement is going to magically help you slim down.

But there are some vitamins, minerals and supplements that may be able to support you in your weight loss journey if you pair them with a healthy diet and exercise routine, says Bill Willis, a biomedical scientist at Ohio State University who conducts research for Examine.com, an independent site that examines the evidence on nutritional supplements.

“There are so many gimmicky, magic-bullet fixes out there that say, ‘Take this, you’ll lose weight,’” Willis says. “Your diet and lifestyle need to be squared away first. Before you consider supplements, do two things. First, get moving. Number two, change your diet.”

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Manufacturers of weight loss supplements don’t have to prove the accuracy of claims on their product labels, so it can be tough to know which ones, if any, are effective and safe, says Mark Huntington, M.D., a family medicine physician and professor at the University of South Dakota Sanford School of Medicine who has studied supplement effectiveness.

In addition, nutritional supplements are hard to study because there can be varying concentrations of the active ingredient in each batch.​​

Vitamin supplements

A multivitamin could be helpful – and certainly won’t hurt – if you have changed your diet to try to lose weight, Huntington says.  

“Anytime you’re trying to lose weight, vitamins are important,” he explains. “If you’re decreasing your oral intake of food, there is potential to have a nutrient deficiency.”  

If you eat a balanced diet, however, a vitamin may not be needed for your weight loss journey.  

Among the different vitamins, B12 has probably received the most attention as a weight loss tool. One study found that vitamin B12 could play a role in fat metabolism. Other studies have linked low vitamin B12 levels to obesity, diabetes and high cholesterol in animals. 

Experts say more research is needed and that there is no conclusive evidence that a vitamin B12 supplement is helpful for someone who already gets enough of the vitamin through food.  

Huntington warns that taking large doses of some vitamins can be toxic.

What is the scientific evidence for weight loss supplements?

A 2021 systematic review published in Obesity analyzed 1,743 clinical studies of vitamins and supplements for weight loss. Another 2021 review in the International Journal of Obesity looked at 121 randomized, placebo-controlled trials.

In both studies, compared to a placebo, some people taking supplements reported small amounts of weight loss. But the researchers said there wasn’t enough high-quality evidence to prove effectiveness, and no supplement was linked to long-term, clinically significant weight loss.

If you want to try a supplement or vitamin for weight loss, keep in mind that they can have side effects, Huntington says. It’s also important to talk to your health care provider before taking a weight loss supplement. 

7 weight loss supplements 

Here are some popular weight loss supplements and the science behind each:

1. Chitosan

Chitosan comes from the exoskeleton of shellfish and is used in medicine to reduce bleeding from wounds. Chitosan supplements are promoted as “fat blockers” that can bind with dietary fats so the body doesn’t absorb them, Huntington says.

According to the Obesity review, one well-designed study showed trial participants taking the supplement lost on average about six pounds.  A few other higher quality trials have suggested that chitosan could reduce total cholesterol as well as LDL “bad cholesterol.”

However, other studies found no benefit, so more research is needed.

Reported side effects include flatulence, bloating, constipation, indigestion, nausea and heartburn.

2. Chromium

Chromium is a trace mineral that plays a role in your body’s metabolism. Chromium supplements are believed to enhance the effects of insulin in the body, and some research shows chromium can improve blood sugar regulation in people with type 2 diabetes.

However, the supplement does not seem to affect blood sugar levels in people without diabetes, according to an Examine.com research analysis. “Even though chromium is a popular dietary supplement, the research on chromium is fairly mixed, and where benefits have been found, they tend to be small or negligible,” the site’s review says. 

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Of six studies on the micronutrient in the Obesity meta-analysis, three had a low risk of bias and only one of those linked it to weight loss ranging from 3 to 6 pounds. “If it works, it only helps a little bit,” Huntington says.

Chromium supplements can cause stomach pain and bloating, and there have been a few reports of kidney damage, liver damage, muscular problems and skin reactions following large doses, according to the National Center on Complementary and Integrative Health.

3. Magnesium

Magnesium is an important mineral necessary for many essential bodily functions, says Madesh Muniswamy, a magnesium researcher and director of the Center for Mitochondrial Medicine at the University of Texas Health Science Center at San Antonio.

Research suggests as many as half of all Americans don’t get enough magnesium. Magnesium deficiency is more prevalent in people who have obesity, diabetes and metabolic syndrome, and it has been linked to chronic inflammation.

A 2020 systemic review of 32 studies found most adults don’t lose weight when taking a magnesium supplement. However, it did help with weight loss in those with a magnesium deficiency, diabetes, obesity or high blood pressure.

You can find out if you’re magnesium deficient by asking your health care provider to run labs to check your magnesium level.

Adults should not consume more than 350 mg per day of magnesium in a supplement, according to the NIH. Large doses can cause diarrhea, nausea, abdominal cramping and, in the event of extremely high intakes, a risk of death from cardiac arrest.

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4. Probiotics/synbiotics

Probiotics are beneficial bacteria that live in your gut and help break down and digest food. You can get them from supplements or from fermented foods like kefir, sauerkraut and apple cider vinegar. 

Early evidence indicates probiotics could be helpful when it comes to weight loss, says Dariush Mozaffarian, a cardiologist, public health scientist and director of the Food is Medicine Institute at Tufts University.

One 2018 review of 15 well-designed trials found that probiotics, either in foods or in supplements, helped overweight and obese people reduce their body weight and body fat. Other trials have linked probiotics to improvements in blood sugar levels. 

Some manufacturers are combining probiotics with prebiotics, a type of fiber that feeds gut bacteria. Mozaffarian says he believes those combinations, called synbiotics, are promising.

“It won’t be magical – the pounds won’t melt away – but if you have a healthy microbiome, you may be more likely to be able to lose weight or at least not gain further weight,” he says.

Although few studies have examined the safety of probiotics, they have a long history of safety, particularly in healthy people, according to the NIH. If you have a weakened immune system, there is a greater risk of negative side effects from probiotics, so you should talk to your health care provider before taking them.

5. Caffeine

Caffeine is a stimulant found in tea, guarana, yerba mate and other herbs that is often added to weight loss supplements. It can give you a jolt of energy, boost your metabolism and increase fat breakdown, Willis says.

“It is an excellent lipolytic agent,” Willis says. “By that I mean it helps liberate fatty acids from our fatty tissues, especially for cardiovascular exercise. It helps to increase fat burning.”

Studies have shown only a moderate weight loss effect, however. The National Institutes of Health says it “may help you lose a little weight or gain less weight over time.”

Willis says caffeine and other fat-burning supplements need to be accompanied by changes to diet and lifestyle. “If your diet and lifestyle isn’t going to be conducive to losing fat, fix that first,” he says. “It won’t help you if you’ve just eaten three double cheeseburgers with an order of fries and a milkshake.”

Many people experience side effects from caffeine such as a rise in blood pressure and heart rate, sleep problems, anxiety or jitteriness or gastrointestinal problems. In high doses, caffeine can cause vomiting, heart palpitations and seizures. The National Institutes of Health recommends no more than 500 mg a day.

People with high blood pressure or heart problems should check with their health care provider before taking a supplement with caffeine.

6. Green tea extract

Green tea contains a class of phytochemicals that are known as antioxidants, Wiley says. Some people believe green tea extracts, sometimes called EGCG, contribute to weight loss by boosting energy expenditure and blocking fat absorption.

A few studies do seem to indicate that green tea extracts could make you burn more calories, even when you’re at rest. But there is conflicting research on whether supplements with green tea extracts can help you actually shed pounds, Wiley says.  If anything, they have only a moderate effect.

Green tea may have other benefits, potentially protecting against heart disease and cancer. Experts warn that large doses could cause liver damage.

7. Berberine

Berberine is a substance found in plants that has a long history of use in Ayurvedic and traditional Chinese medicine.

The most studied benefit of berberine is its ability to improve insulin resistance in people with diabetes, according to The Cleveland Clinic.

Early research also indicates berberine could help with weight loss. A 2022 review of 41 research trials published in Frontiers of Nutrition found that people who took berberine for at least eight weeks experienced significant drops in their weight, and their cholesterol levels also improved.

However, more evidence is needed, because many studies in the review had a high risk of bias, according to the National Center for Complementary and Integrative Health.

Berberine side effects include GI symptoms such as nausea, diarrhea, bloating and constipation. It can also interact with prescription medications. As with all supplements, you should talk to your health care before taking it.

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