Weight Loss Supplements 101: Everything You Need to Know

Medically Reviewed by Anthony Dugarte, M.D., C.S.C.S

The weight loss market in the United States is estimated at tens of billions of dollars, with many consumers spending money on weight loss programs as well as weight loss supplements. Unfortunately, millions of people aren’t aware of the potential dangers and side effects of these products – or if they actually work.

For the most part, experts do not recommend taking weight loss supplements because of their negative side effects, which include jitteriness, an increased heart rate, and insomnia; as well as stomach discomfort, diarrhea, and constipation.

In 2014, the U.S. Food and Drug Administration had issued more than 30 public notifications and recalled several tainted weight loss products, in addition to issuing warning letters and seizing products.

And while some people might see results while taking weight loss supplements, they might gain the weight back once they cease taking them, leaving them back where they started while wasting their money in the end.

According to Allison Wells, a certified personal trainer and a certified nutrition consultant, weight loss supplements typically fall into one or more of these three categories:

Depending on the ingredients in the pill, the effect will vary, said Wells, noting that any source of caffeine will increase metabolism and potentially suppress your appetite.

Industry Background

According to the U.S. Food and Drug Administration, under the Federal Food, Drug and Cosmetics Act – as amended by the Dietary Supplement Health and Education Act of 1994 – dietary supplement firms do not need FDA approval prior to marketing their products.

Thus, ensuring FDA compliance requires only descriptive text indicating that the product is a dietary supplement, the name and address of the manufacturer, the ingredient list, and the net contents dosing of the supplement.

Wells does not recommend any specific weight loss supplement because the industry is inundated with unsubstantiated claims, and very little research has been done on the long-term effects of most of these products.

The products that do have some potential for weight loss success are often taken in conjunction with a low-calorie healthy diet, and regular exercise, Wells noted, adding that “these two factors alone are the most effective way to maintain weight loss, without the negative side effects that often accompany weight loss pills.”

In 2014, the U.S. Food and Drug Administration had issued more than 30 public notifications and recalled 7 tainted weight loss products, in addition to issuing warning letters and seizing products, as well as criminally prosecuted people responsible for marketing illegal diet products.

Who Should Avoid Weight Loss Supplements

Typically, people with a Body Mass Index (BMI) of 30% or higher would be a candidate for a weight loss supplement, Wells said.

Or, someone with a BMI of 27% or higher, if they have a health condition that is better managed with weight loss, such as diabetes or high blood pressure.

If you have any existing health conditions or concerns, it’s best to consult with a doctor before taking any new supplement for weight loss, fat burning or appetite suppression, according to Wells, who noted these products should be avoided by the following:

  • People with heart conditions, seizures or hypo or hyperglycemia should avoid anything with excess caffeine, which many weight loss supplements contain

  • People with gastrointestinal issues, such as irritable bowel syndrome or colitis, because many weight loss pills negatively affect the intestines, gastrointestinal tract and bowels

  • People with diabetes should consult with a doctor before taking weight loss supplements

  • People with a history of eating disorders

Ingredients That Could Be Effective

  • Caffeine: Caffeine is a stimulant that is often added to diet pills. It’s been claimed to increase metabolism, reduce BMI, suppress appetite, and increase energy. It can also cause jitteriness, increase heart rate, and trouble sleeping. The most important thing is to manage your dose and be sure not to take more than 300mg of caffeine per day (this means stimulant beverages and supplements combined).

  • Green Tea Extract: Green tea is a mild stimulant that has also been claimed to promote fat loss. While there is not much research to back this up, high doses can cause stomach pain and constipation.

  • Conjugated Linoleic Acid: This is marketed to help boost metabolism and decrease appetite, though most of the studies were done on animals. Some doctors suggest this supplement is safe in doses of up to 6 grams per day for one year, but other research has shown a negative long-term impact on metabolic health. This is not suitable for anyone with diabetes. Some side effects include stomach discomfort, diarrhea, and constipation.

Most weight loss or fat burner pills work the same by providing significant amounts of caffeine or caffeine-based ingredients to increase the heart rate and body temperature as a way of helping you burn more calories, according to Dr. Annthea Fenwick, an expert in nutrition and owner of Achieving Fitness After 50.

“Some will add an appetite suppressant in addition, to help you reduce how many calories you ingest,” said Dr. Fenwick, adding that most of these products will not tell you how much caffeine they are providing, but it is several times greater than the recommended daily intake.

“The result of too much caffeine can be increased blood pressure, heart palpitations, nausea, lightheadedness, and even increased risk of a heart attack.”

Ingredients That Are Hype

Many weight loss supplements are marketed to have great results, but consumers should be mindful of ingredients that are not proven to work:

  • Garcinia Cambogia Extract: This is a fruit that contains hydroxy citric acid that “may” inhibit fat producing enzymes. “There is no proof that this actually works but is not known to have any negative side effects,” Wells noted.

  • Raspberry Ketones: These claim to help burn fat, but there have been no successful studies done on humans. Some side effects report increased blood pressure and jitteriness.

  • Glucomannan: This is a fiber found in the root of the konjac plant. It absorbs water to form a bulky fiber. This can treat constipation, and possibly slow the absorption of sugar and cholesterol from the gut. It helps in appetite satiation, but side effects include flatulence, bloating, and soft stools. There is insufficient evidence that it aids in weight loss.

Are Weight Loss Supplements Safe?

As caffeine has been proven effective for weight loss, it is one of the most widely included ingredients in dietary supplements that claim to offer weight loss benefits.

Despite companies sourcing natural forms of the stimulant that you may already consume on a daily basis, they may offer quantities that can be dangerous.

Thus, your risk for harm may be more likely if you use a stimulant-containing supplement along with your typical coffee, tea, and soda intake. Also, those with pre-existing medical conditions related to cardiovascular health can be even more susceptible.

According to the FDA, you can limit the risk of harm by keeping caffeine consumption under 400mg daily (3 or 4 cups of coffee).

If you’ve consumed too much caffeine, you may experience side effects like headaches, restlessness, nausea, diarrhea, dizziness, rapid heart rate, high blood pressure, and confusion. Also, rapidly consuming 1,200mg of caffeine can cause seizures and even death.

Given that the chance for adverse effects is considerable, you should avoid consuming stimulant-containing supplements. The risk is not worth the potential benefits.

Always speak with your doctor prior to using any dietary supplements, especially those with high levels of caffeine.

Shopping Tips

  • Do Your Own Research: If you’re looking for a weight loss supplement, do your research, Wells advised. If something claims to be “clinically proven,” see what the clinical evidence is to support it. Notice how many people are included in the studies, what other factors were at play, such as diet and exercise, and what the length of the study was to prove long-term success.

  • Be Skeptical of Articles Sponsored by the Brand: When you’re looking at articles related to the product you’re researching, make sure the article isn’t sponsored by the brand, Wells recommended. “A key tip here is, if there’s a button to click to purchase the product straight from the website, it’s probably sponsored and therefore likely a biased review.”

  • Research Legitimate Sources: Read medical journals and articles from The Mayo Clinic, WebMD, or Medical News Today for more credible sources of information, because these will give you a better idea of any side effects and legitimate research.

  • Determine the Facts: The Office of Dietary Supplements at the National Institutes of Health has an index to help consumers determine some of the facts about supplements.

The Bottom Line

When it comes to trying a weight loss pill or supplement, Wells provided the following 3 important factors to keep in mind before you make a purchase:

  • The supplements that claim successful results are almost solely in conjunction with a restricted-calorie diet and regular exercise. Even the groups that have had success during those trials had minimal weight loss compared to the other individuals with a placebo. Therefore, committing to diet and exercise alone could certainly warrant similar results without the negative side effects that come along with many of these supplements.

  • If you’re trying out a new supplement, weigh the cost, both physical and financial. Most of these have a long list of possible side effects, and there has not been much research proving the effects of long-term use. Taking a pill that may give you a 2% increase in weight loss might not be worth the bowel issues, jitteriness, increased heart rate, or any of the other potential side effects. Remember, this is a money-making market. Everyone is looking for a quick fix or a nudge to get results faster, and it’s typically not sustainable, realistic, or healthy for your body.

  • Consult with your doctor before adding any new supplements to your regimen. It’s very important to understand how they interact with any prescriptions or other supplements you may be taking. You also want to make sure you don’t have any health conditions that would be compromised by using a weight loss supplement.

Losing weight can be a frustrating and daunting process, and it can be tempting to take a pill in hopes of it helping to speed up your results, Wells said.

“The reality is weight loss is a journey, and the pills often have more of a placebo effect or negative effect on your body, than the magic you might be hoping to find in it,” she said, adding, “the more consistent you are with diet and exercise, the more likely you are to see results.”


Alicia Doyle

Alicia Doyle is an award-winning journalist who has covered a wide range of topics about beauty, cosmetic surgery, and procedures. With an affinity for human-interest stories, she has written hundreds of articles about inspirational people and organizations that have a positive impact on people’s lives.

Weight Loss Supplements 101: Everything You Need to Know