Fats are composed of carbon, oxygen and hydrogen. When a hydrogen atom is attached to every carbon atom, the fat is "saturated." It's easy to identify saturated fats—they're naturally solid at room temperature (think lard.) By contrast, unsaturated fats are liquid (most vegetable oils).
Monounsaturated fat (MUFA) may lower the risk for diabetes and breast cancer, while improving heart and lung function. Additionally, they seem to decrease fat stored around your middle, and—bikini season aside—abdominal fat is more unhealthy than fat stored on, say, your thighs. Those "flat belly" diets being touted these days? Their central feature is MUFAs.
MUFA-rich foods include olives, vegetable and nut oils (especially olive and canola), nuts and seeds, avocados, and dark chocolate. But don't devour a pound of chocolate and wash it down with olive oil. Weight reduction is always about burning more calories than you take in, and fats are very high in calories-about 120 calories per tablespoon, give or take. Guidelines suggest that fats should compose roughly 30 percent of our caloric intake, and within those limits, monounsaturated fats may have highly desirable results.
—By Jo Marshall, a food writer in Deephaven, Minn.