The spice: Hot peppers (including cayenne, chili, jalapeño)
How they do it: Pass the Tabasco! People consume about 75 fewer calories after eating red chili peppers compared to after eating bland food, a new meta-analysis of several studies concluded. Researchers at Purdue University also found that chemicals in peppers called capsaicinoids (the origin of the burning sensation) reduce cravings for fatty, salty and sweet foods. (The catch: This was true only for people unaccustomed to the heat, not die-hard chiliheads.) If that's not enough, consider the mounting evidence that when the capsaicinoids reach the gut, they signal receptors to increase the number and activity of the body's "brown fat" cells, which increase core temperature and burn calories faster than usual.
How much to use: At least 1/2 teaspoon of hot peppers per serving.
What to try: Quinoa-Black Bean Chili and Nigella Lawson's Choc Chip Chili