Many manufacturers offer weight loss products containing green tea extract and hoodia. While research shows that both of these supplements may contribute to a weight loss program, neither has been approved by the U.S. Food and Drug Administration for weight loss. Additional clinical studies are needed to conclusively prove or disprove claims made by weight loss supplement manufacturers.

Green Tea

Clinical studies suggest that green tea may boost your metabolism and aid your body in burning fat. According to Rebecca Dobler of Vanderbilt University, green tea promotes heat production, or thermogenesis, in the cells, enhancing energy expenditure and stimulating weight loss. Additionally, green tea may inhibit the digestion of fat in the intestines, according to the University of Michigan Health System.

Hoodia

Many varieties of hoodia exist, but only the rare Hoodia gordonii contains the active ingredient thought to suppress appetite, reports Melissa Divack of Vanderbilt University. This active ingredient, a steroidal glycoside now known as P57, seems to affect the hypothalamus, which regulates hunger and fools your brain into thinking you’re full for up to 24 hours. However, claims that hoodia effectively suppresses appetite are not supported by any solid evidence, warns MayoClinic.com. Also, the rarity of the hoodia botanical has prompted some less than reputable manufacturers to advertise hoodia weight loss products that don’t actually contain any hoodia.