1. Coconut Oil
Why it makes you skinny:
Most oils, including corn and olive, are broken down into fatty acids that circulate through your body after you eat them, allowing hungry fat cells to suck them up and store them. Coconut oil, however, is rich in a type of fat rarely found in other foods, called medium-chain triglycerides (MCTs). "When you eat MCTs, they go straight to the liver instead of going directly into circulation. There, they're burned up like kindling for a fire," says Cherie Calbom, author of The Coconut Diet.
Plus, your body requires extra energy to digest MCTs. Including them can increase your daily burn by 45 calories, says Marie-Pierre St-Onge, Ph.D., assistant professor of nutrition at the University of Alabama at Birmingham.
How to use it:
Spread coconut oil on toast instead of butter, melt it on veggies or use it for sautéing. But don't deep-fry with it; coconut oil breaks down at high temperatures. Look for virgin oil (nonvirgin is processed and tastes nasty) at health-food stores. Beware: Coconut oil is saturated and can raise cholesterol and triglycerides, so alternate it with other oils.