Why dietary supplements for weight loss may be ineffective

There are many weight-loss supplements on the market that claim quick results, but these may be ineffective or lead to harmful side effects.

If you’re trying to lose weight, it may be tempting to try a fad diet or weight-loss supplements. You’re not alone — 15% of adults in the U.S. have used a weight-loss dietary supplement at some point in their lives, according to the National Institutes of Health.

However, while weight-loss supplements may promise fast results, these may not be effective or safe to use. Dietary supplements — including those for weight loss — do not need approval from the U.S. Food and Drug Administration (FDA). Plus, there is conflicting evidence about their effectiveness.

On the other hand, the FDA has approved some medications that are safe to use for weight loss. These are only available via a doctor’s prescription.

Here’s what you need to know about weight-loss supplements and how they compare to prescription medication.

What are dietary supplements?

Dietary supplements for weight loss may come in the form of pills, liquids, or powders and many contain dozens of ingredients, like herbs, plant fibers, or caffeine.

However, unlike prescription medications, these dietary supplements do not need approval from the FDA before being marketed or sold. This means that the FDA does not have to pre-review these products and manufacturers are responsible for making sure their products are safe to use.

While many of these supplements for weight loss may be available to buy, that does not mean they are safe to use. Manufacturers may make untrue claims about their product or include ingredients — such as drugs or active ingredients found in medications — that are not listed on the package.

If a supplement is found to be unsafe, the FDA may then remove it from the market. A list of tainted weight-loss products is available online.

Why weight-loss supplements may be ineffective or harmful

The evidence around weight-loss supplements and ingredients contained in these supplements varies a lot.

The Office of Dietary Supplements says that in many cases, there is insufficient or conflicting evidence around weight-loss products. For example, research may have been conducted on animals or in a lab, but not with actual humans.

Other studies are too short, too small, or of a poor quality, which means the findings do not provide strong evidence to show that products work.

Another issue is that studies may involve an isolated ingredient, but the weight-loss supplement itself contains a combination of ingredients. Plus, variations in ingredients, amounts, and dosages all make it difficult to isolate the effect of one ingredient or to compare studies.

For an overview of evidence for different ingredients found in weight-loss supplements, check out this fact sheet from the Office of Dietary Supplements.

How to recognize potentially tainted products

The FDA has identified some weight-loss supplements that have been tainted with drug ingredients. While some of these have been removed from the market, some tainted products continue to be sold.

To recognize potentially tainted products, the FDA recommends looking out for misleading keywords or phrases like “lose 10 pounds in one week”, “quick fix”, “guaranteed”, “scientific breakthrough”, “quick and effective”, or “totally safe.” These claims may be unfounded or may not have sufficient evidence to back them up.

In general, the FDA advises that any weight-loss claims that sound too good to be true probably are.

Also be wary of products that are marketed in a foreign language, through mass emails, or ones that claim to be an herbal alternative to an FDA-approved drug or medication.

How can prescription medication help with weight-loss?

Unlike dietary supplements, prescription medications are FDA approved for both short-term or long-term use.

Some FDA-approved weight-loss medications include Xenical or Alli (Orlistat), Qsymia, Contrave, and Saxenda. These may work to reduce the amount of fat the body absorbs, lessen appetite, or make you feel full sooner. Many studies have proven their effectiveness when used with a healthy diet and physical activity plan.

For example, a 2012 study in Europe found that people who used Orlistat for two years along with a restricted diet lost more weight than people who only had a restricted diet and took a placebo medication instead. Moreover, in the second year, the people on Orlistat gained less weight than the placebo group.

A 2020 meta-analysis — which reviewed various weight-loss studies in recent years — found that people who used weight loss medication for a year or more typically lost 4% to 8% of their weight. Moreover, they lost up to 6.8% more weight than people who were not using medication.

Some people using these medications may experience side effects like nausea, constipation, or diarrhea, but these are generally mild and will go away with time. For people who experience ongoing side effects, a doctor may recommend changing the dose or medication.

Talk to your doctor if you’re considering supplements

Your doctor or health care provider can help you weigh the risk and benefits of using certain weight-loss supplements. It’s also important to let them know about health conditions or medications you’re on, as the ingredients in supplements can interact with medications and cause unwanted side effects.

Whether you’re considering supplements, a diet, or any other lifestyle change to lose weight, it’s good to talk to your doctor so they can advise you on best practices.

Health professionals recommend that lifestyle changes like eating a healthy diet, eating fewer calories, and physical activity are the best way to lose weight in the long-term and keep the weight off.

When necessary, a doctor may prescribe weight-loss prescription medications or bariatric surgery.

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