After seeing an ad for pants that are laced with caffeine, we asked volunteer Tanya Hakim to wear the pants for two weeks to see if she noticed a difference.
The makers of the garments, Lytess, recommend wearing the pants at least five hours a day for two weeks to see results.
There are plenty of studies that suggest drinking caffeine can increase a person's metabolic rate and burn some calories. As far as wearing it, though, the data doesn't seem to reflect that yet.
Supplement expert Ellen Coleman says whether you wear pants or patches, the only thinning will occur in your wallet.
"Who wouldn't want to put a patch on their skin or put a pair of caffeine-laced bicycle shorts on and do whatever you've continued to do with your diet and exercise and miraculously melt off pounds?" she said. "Weight loss patches or dietary supplements, the companies do not have to prove that the compounds in the weight loss patches are being absorbed."
Regarded as dietary supplements, these products contain stimulants like caffeine, guarana and hoodia, with the intention of being absorbed through the skin. Coleman says that remains unproven.
"The doses of caffeine that you would have to use to increase metabolic rate would be huge and there's no evidence that either garcinia or hoodia promote weight loss, even if you take them by mouth," Coleman said.
Lytess cites a study where testers lost weight after wearing them for a month.
"I looked for the published research demonstrating that and found that the company had volunteers wear the shorts and did these measurements before and after 28 days. But these results have not been published anywhere," Coleman said.
The best advice is to read the fine print.
"All of these products make the claim that this product works best when combined with cardiovascular exercise and a calorie-restricted diet," Coleman said.
After two weeks of wearing the caffeinated pants in our admittedly unscientific experiment, Hakim said she hasn't lost an ounce.
"I say throw away the shorts, follow the exercise program and the calorie-reduced diet and that's how you lose body fat," Coleman said.
Other information provided by Coleman on ingredients found in weight loss patches and also caffeine pants:
Fucus - contains iodine. In theory, affects thyroid and helps regulate metabolism - no evidence it promotes weight loss.
Guarana - herb with a high caffeine content - has a mild thermogenic effect.
Hoodia - thought to curb appetite. San tribe chewed stalks to decrease hunger and thirst while hunting. No evidence it promotes weight loss.
Garcinia or hydroxycitrate - thought to decrease fat synthesis, no evidence it promotes weight loss.
Lytess Slimming (Caffeine) Bike Shorts
Clinical studies have shown size reduction up to -1.2 inches on thigh and up to -2.1 inches on hips after 21 days. Guaranteed for 30 washes. Microencapsulated fat-mobilizing caffeine and hydrating shea butter woven fabric release as it rubs against your skin for all-day slimming and softening.
Even if ingredients affect appetite and weight, there is no evidence they're getting into the body by the patches or shorts. Compounds must have a low molecular weight (be very small) to be absorbed through the skin. Also, although a drug works when swallowed, it doesn't mean it works when placed on the skin.