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Understanding Weight Loss Supplements, Pills, Shakes and Vitamins

Weight loss supplements come in many forms, including tabletspillsgummychews and vitamins, as well as meal-replacement barsdrinks and shakes.

They all claim to make it easier to lose weight ― some even promise rapid results ― but it’s important to know that not all weight loss supplements are created equal.

Different products contain different ingredients, with different modes of action and different levels of effectiveness.

For example, some weight loss supplements work to curb hunger, helping you eat fewer calories. Fat blockers block the absorption of some fat, helping you take in fewer calories. And fat burners (also called metabolism boosters) claim to boost metabolism, helping you burn calories faster.

If you’re considering using a supplement to lose weight, you may have some concerns, such as:

  • Are weight loss supplements good or bad for you?
  • Do they really work?
  • Are they safe?
  • Which supplements work best?

These are all excellent questions. This article will look at various types of weight loss supplements, and the pros and cons of each. You’ll also learn what’s known about the safety and effectiveness of many ingredients that are commonly used in supplements.

Click a link in the Table of Contents to skip to a question. Let’s start with the question that probably brought you here:

Do weight loss supplements really work to help you lose weight?

This question is tricky, because the answer can be either yes … no … or sometimes, depending on which supplement you are talking about, as well as your expectations.

There are no miracle pills that will make you magically shed pounds. Supplements are intended to be part of a lifestyle that allows you to lose weight in a healthy, sustainable way.

Any product that promises radical weight loss, quick results, or other over-the-top claims should be viewed with skepticism. When weight loss supplements sound too good to be true, they usually are. Losing weight is a process. It begins with eating a healthy, balanced diet and being physically active.

Before you begin a weight loss supplement plan, talk with your doctor or healthcare provider to make sure the ingredients won’t interact negatively or interfere with any medication you are taking. This is especially important if you have a medical condition such as high blood pressureHashimoto’s diseaseliver damage or hypothyroidism, or if you are diabetic or  breastfeeding.

Having said that, good news is: Yes, there are weight loss supplements that actually work. There are supplements that are safe, natural and effective. You just have to know what to look for ― and what to look out for. Which brings us to …

What you need to know before you begin a weight loss supplement plan

Weight loss supplements can vary greatly in terms of quality based on a number of factors. We cannot stress enough how important it is to know what you are spending your money on and, even more importantly, what you are putting in your body.

Despite claims to the contrary, dietary supplements are not FDA approved. Under the Dietary Supplement Health and Education Act of 1994, dietary supplement makers do not need to be FDA approved to market their products. Rather, the government relies on the honor system, leaving it to companies to make sure their products are safe and that any claims made about such products are true.

Here are a few simple questions that can help distinguish between a supplement that really works to help you safely lose weight and one that’s a waste of money ― or, even worse, one that’s potentially bad for you.

Where was it made?

Many supplements sold online and in retail stores are made in China and other countries that have low standards for purity and safety. At best, these products are loaded with useless fillers that make them ineffective. At worst, they can contain harmful contaminants such as pesticide residues and heavy metals including mercury, cadmium and arsenic. Your best bet is to choose supplements that are sourced and made entirely within the U.S.

Are there any known side effects?

Weight loss is a multi-billion-dollar business. The lure of big profits attracts unscrupulous companies selling products that contain dodgy ingredients known to cause unpleasant, sometimes dangerous side effects, ranging from liver failure to heart attack. We will review the known side effects of popular weight loss supplements and ingredients in the next section, so you know which to avoid.


While the FDA does not approve weight loss supplements to affirm their safety and effectiveness, it does offer one type of supplement ingredient regulatory classification: “generally recognized as safe,” commonly referred to as GRAS. An FDA-GRAS designation means an ingredient is generally recognized by qualified experts in the scientific community as safe to consume.

Are there clinical studies or other scientific research to prove the product’s effectiveness?

With such an enormous market size for weight loss supplements, combined with scarce government regulation or oversight, it’s no surprise that the market is flooded with smoke-and-mirrors products that offer no evidence or proof of efficacy. Look for reviews that look at all current research into an ingredient’s effectiveness as a weight loss supplement ingredient, compiling statistics.

Does it matter where you buy weight loss supplements?

The short answer here is, no. For the most part, you will find the same supplements at stores such as Whole FoodsGNCCVSVitamin ShoppeCostcoWalmartWalgreens and Target as well as online at Amazon and manufacturer’s websites.

Be careful to review the ingredients (we’ll talk more about weight loss supplement ingredients below) as well as the terms of any online offer. Some online marketers offer “free trials” that are not actually free. Many of these trial offers are designed to capture your credit card information and put you into a monthly billing subscription cycle.

Be especially wary of weight loss supplements that rely on celebrity endorsements. There’s little chance that celebrities use the products they endorse. Most celebrities have fitness trainers and nutritionists to help them lose weight ― and even if they do use the product, it’s certainly no guarantee that a supplement is safe.

Now that we’ve covered the basics, let’s dive in for a closer look at what’s inside popular slim-down supplements.

A review of common weight loss supplement ingredients and modes of action

As stated above, supplements come in a variety of forms, including pills and tabletsready-to-drink shakes and drinkspowders you can mix to make your own shakes and drinks, as well as meal-replacement bars. The particular form you choose doesn’t matter as much as the active ingredients it contains, so we will focus on ingredients rather than specific forms.

Dietary supplements can contain numerous ingredients — everything from natural herbsherbal extracts and fiber to laxativescaffeine and synthetic chemicals.

Figuring out which weight loss supplement ingredients really help you lose weight safely is complicated, especially since these ingredients are often mixed together without much research into the safety of the combination or studies to provide evidence of their effectiveness.

When choosing a weight loss supplement, you will have to weigh the benefits and dangers. With that in mind, here’s the skinny on some common ingredients:


The claim: Caffeine is frequently included in over-the-counter diet pills like Hydroxycut and weight loss supplement stacks sold both in stores and online. This is, in part, because caffeine is believed to boost metabolism and increase fat burning, as well as for the energy boost caffeine provides feels good.

You may be surprised to see caffeine listed in a review of weight loss supplement ingredients. That’s because many supplement companies downplay the role of caffeine in their products. They don’t want you to know that their “secret ingredient” is a stimulant you can get from an ordinary cup of coffee or a neon-green energy drink.

Does it work? While caffeine can boost metabolic rate and fat burning, the effects are short lived. People very quickly build up a tolerance to caffeine’s fat-burning properties, and it stops working. Since most people consume caffeine on a regular basis, it is unlikely to have any significant or lasting impact on weight loss.

According to the Mayo Clinic, “… there’s no sound evidence that increased caffeine consumption results in significant or permanent weight loss. Some studies looking at caffeine and weight were poor quality or done on animals, making the results questionable or hard to generalize to humans.”

Again, one reason so many weight loss supplements contain caffeine is simply that caffeine provides an energy boost that feels good and encourages users to keep taking the supplements.

Is it safe? Most of us are aware of the pros and cons of caffeine. Caffeine is both good and bad for you. Caffeine consumption has been shown to have some health benefits such as reducing the risk of diabetes and treating headaches.

On the other hand, Caffeine is a stimulant. Caffeine stimulates the central nervous system. Too much caffeine might cause jitters, insomnia, nausea, diarrhea and increased blood pressure. What’s more, caffeine is a drug, and like any stimulant, it can become physically addictive to the point where you can suffer withdrawal symptoms if you stop using it.

Garcinia Cambogia

The claim: “Lose weight up to 3 times faster!” Sometimes mistaken for an herb, garcinia cambogia is a fruit native to Indonesia. Marketers claim it can inhibit a fat-producing enzyme in the body and increase levels of serotonin, potentially helping to reduce cravings and suppress appetite. In other words, it is marketed as an appetite suppressant.

You may have seen Dr. Oz promoting Garcinia Cambogia on his show in 2012. Dr. Oz is no stranger to weight loss fads. He’s done show pieces on everything from raspberry ketones to a powder weight loss supplement you sprinkle on food. Despite Dr. Oz’s zeal for the magic powder, the FTC ordered the company behind the product to pay $26.5 million dollars to settle charges that they deceived consumers. So we have to take his enthusiasm for garcinia cambogia with a grain of salt.

Does it work? Based on studies conducted so far on garcinia cambogia, there is no clinical evidence to support its effectiveness as a weight loss supplement ingredient. A 2011 review that looked at 12 studies on garcinia cambogia stated the following conclusion:

“The evidence from RCTs [randomized clinical trials] suggests that Garcinia extracts/HCA generate weight loss on the short term. However, the magnitude of this effect is small, is no longer statistically significant when only rigorous RCTs are considered, and its clinical relevance seems questionable.”

Is it safe? WebMD reports garcinia is “POSSIBLY SAFE for most people when taken by mouth for 12 weeks or less,” and adds that when you take garcinia cambogia, “you might get: dizziness, dry mouth, headache,” and “upset stomach or diarrhea.”

Consumer Reports says, “Garcinia cambogia has been linked to mania, a condition marked by euphoria, delusions, and overexcitement.” It goes on to say, ”… other research has linked the herbal remedy to health problems that include jaundice, elevated liver enzymes, liver damage requiring a transplant, and one death from liver failure.”


The claim: Glucomannan is fiber extracted from the Konjac root. It is ground up and sold as a weight loss supplement pill, tablet or capsule, as well as in powder form.

Glucomannan is marketed as a hunger-control supplement. Sometimes sold as “Konjac Root” or simply “Glucomannan,” it also is the active ingredient in various name-brand products, including Lipozene, whose makers say the fiber “has the ability to absorb up to 200x’s its own size when in water … and creates a feeling of fullness that lasts for hours,” helping users to “control calories.”

Does it work? A systematic review and meta-analysis of randomized clinical trials involving glucomannan concluded that, “The evidence from available randomized clinical trials does not show that glucomannan intake generates statistically significant weight loss.”

One clinical trial, published in the Journal of Obesity in 2013, concludes, “… glucomannan supplements (3.99 g daily) were well tolerated but did not promote weight loss in overweight and moderately obese individuals consuming self-selected diets and maintaining usual physical activity patterns. Other outcomes such as body composition, hunger/fullness, and lipid and glucose parameters also were not significantly altered.”

Is it safe? Users have reported adverse reactions including abdominal discomfortflatulencediarrhea and constipation. In 2010, Canada’s public health department, Health Canada, issued a public warning, stating that products containing glucomannan, “have a potential for harm if taken without at least 250 ml or 8 ounces of water or other fluid,” also noting, “… these products should not be taken immediately before going to bed.”

Green Tea Extract

The claim: Popular in many weight loss supplements, proponents of green tea extract say its main antioxidant, ECGC, can speed up fat burning, especially belly fat. They say it works by increasing activity of a hormone called norepinephrine that helps you burn fat.

Does it work? Drinking green tea has proven health benefits, so it would make sense that supplements containing green tea extract would have similar benefits.

But does green tea extract actually work to help you lose weight?

One review concluded that research suggests there is some evidence that an EGCG-caffeine mixture has a small positive effect on weight loss and weight maintenance, while admitting that there have been inconsistencies in outcomes.

Another review said that no conclusion can be drawn about ECGC’s effectiveness as a weight loss supplement ingredient based on current evidence. The authors also said that while green tea extract has been shown in some studies to increase fat oxidation at rest and during exercise, these results also have not been consistent.

The review concludes, “Overall, there are more studies that demonstrate positive effects on resting fat metabolism when green tea extract is ingested.”

Is it safe? Green tea is generally harmless. It’s packed with catechins, an antioxidant compound that, in proper doses, delivers health benefits that include lower cholesterol and reduced risk of heart disease and cancer. But when consumed in high concentrations, such as those found in some weight loss supplements, over extended periods, it can have a disastrous side effect known as herbal hepatotoxicity ― chemically induced liver damage.

These findings prompted the American College of Gastroenterology to release recommendations in 2014 about green tea extract intake, saying it can be toxic and cause liver failure at high doses.

Gut Sensory Modulation

The claim: Technically, Gut Sensory Modulation (GSM) is not an ingredient but a patented mode of action used in a weight loss supplement called Lovidia. The claim is that GSM uses the science of nutrient sensing to reduce hunger so that users eat fewer calories, making it easier to lose weight.

GSM leverages the role of food sensors in controlling calorie intake. Specifically, specialized cells called enteroendocrine cells located in the lining of the gut release several hormones into the circulation. These hormones include peptide YY (PYY) and glucagon-like peptide-1 (GLP-1), which signal satiety to the brain ― meaning they tell your brain when you’ve eaten enough.

Taken with meals, GSM uses natural, FDA-GRAS food-grade nutrients to activate the sensors in your gut to release more PPY and GLP-1 than would be released by eating food alone.

Does it work? Unlike many weight loss supplement ingredients, GSM has been tested in multiple double-blind, placebo-controlled, clinical studies on human subjects, and the scientific evidence so far is promising. For example, in one study with 220 subjects, the number of subjects reporting reduced hunger in the GSM group was statistically significant compared with the placebo group.

In another multi-site clinical trial, 52 subjects used GSM and periodic calorie restriction. Participants were instructed to take the GSM daily and to restrict their daily calorie intake to 500 calories for three non-consecutive days each week, with no calorie intake constraints for the other 4 days of the week. Subjects reported an average weight loss of 4 pounds after their first week and 9.4 pounds after 5 weeks. Significant improvements in indicators of metabolic and cardiovascular health were also observed in most of the subjects.

Is it Safe? Again, in regard to safety, GSM has significant advantages over most other weight loss supplement ingredients. That’s because the only ingredients in the formulation are natural, FDA-GRAS food-grade nutrients. There’s nothing artificial, no caffeine or stimulants, and no dangerous fat blockers. No safety flags were notedin clinical trials. The only side effects were positive, as GSM was shown to help reduce blood pressure as well as improve glucose control and blood lipids.


The claim: Raspberry ketones were all the rage in weight loss supplements after Dr. Oz did a segment on his show called “Raspberry ketone: Miracle fat-burner in a bottle,” in 2012. The primary claim is that ketones help to break down fat cells, so you burn fat faster. In other words, it is marketed as a fat burner/metabolism booster.

Does it work? Some research in trials on rodents and in test tubes showed that raspberry ketone might increase some measures of metabolism as well as affect a hormone in the body called adiponectin that affects the rate at which the body burns fat.

But there is not a single study on the effect of ketones on weight loss in humans and NO reliable scientific evidence that proves raspberry ketones improve weight loss when taken by people. The concentrations used in test tube testing cannot be scaled for testing in the human body, particularly through oral supplementation. Similarly, dosages used in rodent testing have been referred to as “insanely high,” with no chance of replication on human subjects.

Is it safe? Regarding possible side effects and dangers, Web MD states, “There isn’t enough reliable information available to know if taking raspberry ketone alone is safe. There are some concerns about the safety of raspberry ketone because it is chemically related to a stimulant called synephrine. Therefore, it is possible that raspberry ketone might cause jitters, increase blood pressure, or rapid heartbeat. In one report, someone who took raspberry ketone described feelings of being shaky and a pounding heart beat (palpitations).”


The claim: Orlistat occupies a unique place among weight loss supplement ingredients. Unlike ingredients such as herbs and herbal extracts that are not subject to being FDA approved, Orlistat is an approved drug for the treatment of obesity. At a lower dose, Orlistat is marketed as a weight loss pill, under the brand name Alli and is available  over-the-counter in the United States.

Orlistat is a lipase inhibitor. Orlistat works by blocking the enzyme that breaks down fats in your diet, leaving them undigested. This undigested fat passes out of your body (more about this later), helping you absorb fewer calories.

Does it work? In short, yes. Data from clinical trials shows that people given Orlistat in conjunction with lifestyle changes, such as healthy eating and exercise, lose an extra 4.5 to 6.5 pounds over the course of a year than those not taking the drug. So, Orlistat is proven effective in aiding weight loss; albeit with very modest results. But it does not block the absorption of calories from sugar and other non-fat foods, so it works best on people who eat a high-fat diet.

Is it safe? This is the big question with Orlistat: Is the moderate weight loss boost worth all the adverse side effects that come with taking the drug? For one, Orlistat can interfere with the absorption of fat-soluble vitamins, including A, D, E, K, so users run the risk of nutritional deficiency. But this is the least of users’ concerns when taking Orlistat.

Much more worrisome is Orlistat’s pronounced and well-documented gastrointestinal side effects. Web MD states, “Fatty/oily stool, oily spotting, intestinal gas with discharge, a feeling of needing to have a bowel movement right away, increased number of bowel movements, or poor bowel control may occur.” These side effects have put Orlistat’s suitability as an OTC weight loss supplement in question. The consumer advocacy group Public Citizen has repeatedly challenged Orlistat’s over-the-counter approval on grounds that it is not safe.


The claim: A number of vitamins and minerals are often used in weight loss supplements, including vitamin B-12vitamin D and calcium. You may see claims that supplementing vitamin B-12, for example, will help boost your metabolism and burn fat away, or that calcium increases the breakdown of fat in your cells.

Does it work? While there are many health benefits of taking a multivitamin, there is not enough conclusive evidence so far, based on clinical trials, that specific vitamins or minerals are effective to promote weight loss.

Is it safe? Taken as specified, vitamins are generally considered safe and beneficial to your overall health and wellbeing. After all, your body needs vitamin B-12 to support the function of your nerves and blood cells, calcium to support strong bones and muscles, and vitamin D to absorb calcium and keep your bones strong. We just need more clinical trials before we can establish the effectiveness of these vitamins as weight loss supplements.

Summary and conclusion

Dietary and nutritional supplements do have value as one aspect of a sensible weight loss plan with healthy eating, diet and exercise at its core.

However, scientific research involving clinical trials shows that many common weight loss supplement ingredients, including those in popular, brand-name products, lack evidence to prove their efficacy. What’s more, many of these ingredients have been shown to cause side effects, including some that can pose serious dangers to health.

The bottom line? Have realistic expectations. Avoid quick fixes and drastic diets. Look at losing and maintaining a healthy weight as a lifestyle, not a short-term goal. And, above all else, be safe. Before taking a weight loss supplement, be sure to discuss the pros and cons with your doctor or health care provider.