Beware an unproven 'nutritional patch' that is taking off in popularity.

A weight-loss patch is drawing criticism for making unsupported claims and for containing unspecified quantities of ingredients which can be dangerous if misused.

The Thrive DFT is a sticker worn on the upper arm which is said to suppress appetite and improve energy. It is marketed alongside a protein shake mix and supplements – "the Thrive experience" – at a cost of between $143 and upwards of $200 a month.

The products are sold by American company Le-Vel and are available locally via home-based distributors, using a multi-level marketing scheme similar to Isagenix and Herbalife.

The three-part "Thrive experience" consists of supplements, a protein shake, and the DFT patch.

The company claims the stickers use "transdermal vitamin technology" to transmit nutrients and stimulants (including green coffee extract, garcinia cambogia, CoQ10 and white willow bark) through the skin and into the bloodstream, but New Zealand experts are wary.

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Dr Shaun Holt, the medical director of HoneyLab, warns there are many reasons to be wary of the Thrive DFT patch, which is not supported by clinical trials. "Best case is that it is a waste of money, worst case is that it is dangerous," he says.

The Thrive DFT weight-loss patch is claimed to be a weight-loss game-changer.

There have been 16 "adverse health events" associated with Thrive reported to the US Food and Drug administration since 2013, including abdominal pain, headaches and fatigue. Three involved hospitalisation.

"I would be very sceptical that sufficient levels of the ingredients would pass through the skin," says Dr Holt. "There are no studies to confirm the levels that enter the bloodstream, if any."

However, if sufficient levels of the ingredients were absorbed by the body, it could be dangerous.

"Some of the ingredients are just bizarre. CoQ10 can lower blood pressure if the dose is high enough. Willow bark extract is basically aspirin. Safety is a real concern. If high-enough levels get into the bloodstream, the safety of this is not known without clinical trials," says Dr Holt.

"And something that really annoys me is the disclaimer on the label to seek advice from a health professional on the product. They have not done trials, health professionals do not know the levels, if any, getting in the body and so cannot advise."

Consumer New Zealand head of research Jessica Wilson also cautions against buying Thrive products. "We haven't seen any substantiation of the claims they are making," she says. "It's very expensive and you'd be better off buying real food.

"Our advice would be for consumers to steer clear."

The "Thrive experience" is claimed to help in these areas: weight management, cognitive performance, digestive and immune support, healthy joint function. It is also said to calm general discomfort and be "age-defying".

"Thrive by Le-Vel is something that's hard to explain, and challenging to describe... it's something that can only be experienced," says the website.

Of the patch ingredients, only green coffee extract has been shown to have any weight-loss effect, and there are "big question marks" around the research which supports it, says Dr Holt.

"Some diet products in the past that also claimed to work by speeding the metabolism had serious side effects, even death."

Users of the product, who call themselves Thrivers, report immediate and near-miraculous improvements in their health when they start using the patches, "lifestyle mix" and supplements.

Although the products are marketed as an "8-week Thrive experience", users on Facebook claim to have been using the product for two and three years at a stretch. Aucklander Taryn Crewe has been using the products for two years and says as a result she has more energy and recovers more quickly after exercise.

"Because I was feeling so good I started to exercise more and make better health choices, and as a result I have lost 6 kilograms and 8 cm around my waist," she wrote on the Le-Vel Facebook page. "This is the easiest and most effective program I have ever tried – I'm thriving, my husband is too and we love it!"

Attempts to contact representatives of Le-Vel have been unsuccessful. One email triggered an automatic response intended for customers who want to share their experiences. It said, "It is important to understand that our products are not intended to help, treat, mitigate or cure any type of disease or disorder. If your testimony contains ANY mentions of a disease, disorder, medical condition, prescription medication, long-term health problem, or persistent/long-term discomfort, it will not be posted."

Have you used the Thrive DFT patch or other Thrive products? Get in touch with us by emailing life.style@fairfaxmedia.co.nz.