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Wouldn’t it be awesome if all you had to do to reach your goal weight was slap a patch on your skin? Manufacturers of weight loss patches would like you to believe this works. But, like lots of other lose-weight-quick schemes, it’s probably too good to be true.

Weight loss patches, in theory, are similar to weight loss pills. But instead of being taken in an oral supplement, the active ingredients penetrate your skin via the patch. From there, they move into your bloodstream and, allegedly, can work their fat-melting magic.

Skin patches (also called transdermal patches) aren’t new. They’ve long been used to treat a range of health conditions. However, there are a few reasons to be skeptical of weight loss patches:

  • Many substances that claim to promote fat loss aren’t that helpful — and they can even be dangerous.
  • Receiving these substances via a patch hasn’t been shown to make them work any better.
  • Herbal remedies, including weight loss patches, aren’t regulated by the FDA, so there’s no evidence they actually work.
  • Because weight loss patches are unregulated, they could contain sketchy or even dangerous ingredients.

If you’re still thinking that maybe — just maybe! — a weight loss patch is a good choice, be aware that most patches contain a cocktail of ingredients, some of which might not even be listed on the label.

We’ll walk you through some of most commonly used active ingredients found in popular patches — and hopefully convince you to steer clear.

How they work

Popular brands, like the Thrive weight loss patch, use green coffee bean extract, which comes from raw, unroasted coffee beans. It contains a substance called chlorogenic acid, which has shown to possibly prevent weight gain (in mice, though).

Green coffee bean extract also contains caffeine, which, research has shown, may help with weight loss. So, sounds kinda promising?

Side effects

Green coffee bean extract has some of the same side effects as drinking coffee: upset stomach, anxiety, headaches, and nausea. But since patches containing green coffee bean extract haven’t been studied, the exact side effects are unknown.

Are they BS?

According to a 2011 review of studies, green coffee bean extract might give your weight loss efforts a slight edge. But again, patches containing green coffee bean extract haven’t been studied.

There’s no way to know if green coffee bean extract works for weight loss in the long term. And remember: Weight loss patches aren’t regulated by the FDA, so you won’t know exactly what’s in them.

How they work

Hokuto mint (also called Japanese mint or corn mint) contains menthol, which gives it that minty smell. Websites that sell Hokuto mint patches claim that the patches block the body’s absorption of sugar and starch so they can’t be stored as fat.

Side effects

Hokuto mint is sometimes used as a flavoring, like in toothpaste, but there has been little recent research on applying it to your skin.

It’s often sold as an essential oil, and it’s generally not a good idea to apply essential oils to your skin unless they’re significantly diluted. But the jury is still out on how it would react as a patch.

Are they BS?

Probably. There’s no research on the weight loss claims around Hokuto mint. And since weight loss patches aren’t regulated by the FDA, you won’t know exactly what you’re getting if you use one.

How they work

Acai berry is packed with antioxidants, which could help fight inflammation, but there’s no evidence acai berry patches contribute to weight loss.

Side effects

Acai is generally considered safe, at least in fruit or juice form. But it could affect the results of an MRI. So if you’re using an acai patch and you’re scheduled for a test, let your doctor know.

Are they BS?

There’s no credible evidence that acai berry — as a fruit, a juice, a pill, or a patch — can help you lose weight, according to the National Institutes of Health (NIH).

Also, weight loss patches aren’t regulated by the FDA, so you never know what’s really in your acai berry weight loss patch. In one instance, a mislabeled acai berry supplement containing contaminants landed a 22-year-old man in the hospital.

How they work

Green tea and green tea extract are known to contain powerful antioxidants. Businesses that sell green tea weight loss patches claim that the patches ramp up your metabolism to boost calorie-burning, as well as stop new fat from being absorbed by your cells.

Side effects

There’s no research on side effects of green tea weight loss patches. However, drinking green tea is perfectly safe. But thanks to the caffeine, green tea can mess with your stomach and cause nausea or constipation. It can also spike your blood pressure.

Are they BS?

Probably. Some research has found that drinking green tea or taking green tea extract may boost your metabolism slightly. But a review of studies on green tea and weight loss found that weight loss amounts were small and “not likely to be clinically important.”

Plus, there hasn’t been any research done on green tea weight loss patches, so there’s no evidence that they help you lose fat. And since the patches aren’t regulated by the FDA, you won’t know exactly what’s in them.

How they work

The herb ephedra, also called ma huang, was in dietary supplements in the 1990s. Some research has found that ephedrine can boost metabolism (especially when taken with caffeine) and increase calorie burn. It also seems to spur the body to burn more fat.

Side effects

Ephedra is straight-up dangerous: The FDA banned dietary supplements containing ephedrine in 2004.

According to the NIH, it’s tied to a higher risk of stroke, could worsen heart or kidney disease, and can even increase the risk of seizures in some people.

It might also make you feel anxious, restless, shaky, or dizzy; cause dry mouth or nausea; or make it harder to sleep.

Are they BS?

Ephedra has been shown to contribute to short-term weight loss, according to a 2003 summary of the evidence. Buuuuuut… ephedra is so dangerous that the FDA banned it from being used in dietary supplements.

There’s no research on whether ephedra patches work or are safe, because this isn’t a substance anyone should be using. And since they aren’t regulated by the FDA, you won’t know what’s really in them. So let’s avoid this one, shall we?

How they work

Bitter orange extract comes from citrus like the Seville orange. It contains a stimulant called synephrine, which is similar to ephedrine. Bitter orange extract patch manufacturers say it can suppress appetite, burn fat, and help you burn more calories.

Side effects

Research on the possible side effects is inconclusive. But according to the NIH, there have been some cases of increased heart rate, increased blood pressure, heart attack, or stroke after people used products containing bitter orange.

Are they BS?

There are no studies on the effectiveness of bitter orange weight loss patches. The NIH notes that bitter orange may increase metabolism — but the side effects probably aren’t worth it. And since weight loss patches aren’t regulated by the FDA, you won’t actually know what’s in it.

How they work

Flaxseeds contain fiber, which can make you feel full, so you might take in fewer calories overall. They’re also rich in omega-3 fatty acids, which can work as an anti-inflammatory.

Side effects

Flaxseeds and flaxseed oil are generally safe to consume. But because weight loss patches aren’t regulated by the FDA, a flaxseed oil patch may contain other ingredients that could have side effects.

Are they BS?

Eating flaxseeds will give you a healthy dose of fiber that could decrease your appetite, but since you can’t absorb fiber through your skin, you won’t reap that benefit from a patch.

There’s also no evidence that the omega-3s in flaxseeds will actually help you lose weight.

How they work

Fucus vesiculosus, a type of brown seaweed, is said to help with weight loss by promoting healthy thyroid function.

Side effects

Fucus vesiculosus might affect your thyroid… but probably not in a good way. It contains large amounts of iodine, which could worsen existing thyroid conditions like hyper- or hypothyroidism. It might also make it harder for your blood to clot.

Plus, the seaweed could potentially contain heavy metals that could be toxic in large amounts.

Are they BS?

The research on Fucus vesiculosus is pretty limited. One study found that the seaweed helped prevent rats from gaining a lot of weight in some cases — but that doesn’t mean it’s safe or effective for humans.

And, as with all weight loss patches, these aren’t regulated by the FDA.

How they work

Both guarana and yerba mate contain caffeine. It’s a stimulant, so it can boost your energy, but patch manufacturers also claim both herbs can help you burn more calories and melt more fat.

Side effects

The FDA doesn’t recommend consuming more than 400 milligrams of caffeine per day. Consuming more than that can cause anxiety, nausea, headaches, and increased heart rate or interfere with sleep. In really high doses, it could even cause seizures.

Are they BS?

Patches made with caffeine-rich herbs like guarana or yerba mate might help you burn a few more calories, but they could also leave you feeling lousy.

Plus, your body will get used to the caffeine dosage over time, so you might find you need more and more to continue reaping the same benefits — and that much caffeine could be unsafe.

How they work

L-carnitine is an amino acid found in high protein foods like red meat, poultry, milk, and beans. It helps move fatty acids into your cells, where they can be burned for energy. Patch manufacturers claim that getting more of it could help you burn more fat.

Side effects

L-carnitine is generally considered safe, but the NIH notes that doses of 3 grams or more per day may cause side effects, including nausea, diarrhea, and abdominal pain.

Are they BS?

It might seem like an L-carnitine supplement or patch could help you lose more weight, but there’s no research specific to the patches. And a small 2000 study found that L-carnitine supplements had no effect on weight.

Weight loss patches aren’t regulated by the FDA. They could contain unsafe ingredients or high doses of questionable substances. If that’s not reason enough to be wary, there’s also zero evidence that they’re a safe or effective tool for weight loss.

If you still want to try one, you’ll have the best chance of success using a patch made from caffeine-containing ingredients like green tea extract, green coffee bean extract, guarana, or yerba mate. But they’ll only help you burn a few more calories, and they may have unpleasant side effects or contain other harmful ingredients.

In short, even patches with potentially beneficial and seemingly safe ingredients probably aren’t worth it. They won’t contribute much to your weight loss efforts — and they could put your health at risk.