Fearing all fat is a thing of the past. Monounsaturated fatty acids (MUFAs) actually help you lose weight, not gain it. When researchers asked women to switch to a 1,600-calorie diet high in MUFAs, they lost a third of their belly fat in just 4 weeks. Sprinkle a handful of nuts on your salad, drizzle a tablespoon of olive oil over steamed veggies, or mash a quarter of an avocado onto your breakfast toast.