Various purported fat loss supplements and foods include: conjugated linoleic acid, ginseng, glucomannan, green tea, hydroxycitric acid, L-carnitine, psyllium, pyruvate, St.
John’s wort, chromium, calcium, chitosan, ephedra, caffeine, guar gum, many other herbal products in naturopathic and complementary medicine, plus illegal steroids and similar compounds such as clenbuterol.
Most of the supplement products have no evidence of efficacy, although it is true that some common foods and supplement derivatives have experimental support for minor effects on appetite and metabolism — chili pepper, caffeine and green tea, for example. Products like amphetamines and their derivatives, and anabolic steroids, are likely more potent in this regard, but more hazardous at the same time. The FDA has banned most over-the-counter products in this category. Prescription drugs may still contain registered weight-loss products like sibutramine.
Thermogenesis means the production of heat, and that’s how some fat burners are supposed to work — by “heating up” your metabolism by causing your heart to beat faster.
In one recent review study, the author noted that “there is no strong research evidence indicating that a specific supplement will produce significant weight loss greater than 2 kg (4.4 pounds), especially in the long term.”
Chili Pepper: Chili pepper has an active ingredient called capsaicin, which is not only responsible for the hot taste, but also for a slight thermogenic effect.
However, like all “fat burners,” this is only a small effect and you won’t lose that excess weight by eating lots of chili.
Caffeine: Caffeine ramps up metabolism by increasing heart rate and the adrenaline system, producing an amphetamine-like effect. Caffeine does seem to have genuine weight-loss potential, but the doses required to have a significant effect may not be tolerated by many people, and may even be hazardous.
In fact, the FDA banned a supplement containing ephedra (a botanical substance with amphetamine effects) as well as caffeine and ephedra together because of possible adverse heart and cardiovascular reactions.
Green Tea: Green tea, in particular, seems to have reliable evidence for some weight-loss effect, even if small. Green tea catechins might act in concert with the caffeine in green tea to exert some fat-burning effect. However, a word of warning is appropriate. Green tea extracts in supplements have been associated with serious liver damage. Drinking the beverage is likely safe but excessive consumption is probably not a good idea.