Capsaicin, an antioxidant in chiles, thwarts food spoilage and may protect blood vessels. It also makes peppers hot—in more ways than one (hence the spicy folklore that piquant peppers rev up sexual desires). Studies show that capsaicin increases the body’s metabolic rate and may stimulate brain chemicals that help us feel less hungry. In a 2005 study in the International Journal of Obesity, people ate 16 percent fewer calories at a meal if they sipped tomato juice spiked with hot-pepper extract (versus plain tomato juice) a half hour earlier.