ince the epic fail of the fat-free craze of the ’80s and ’90s, we’ve learned a lot. The hope was that by cutting fat from our diets, we would trim inches from our figures. Instead, the exact opposite happened: Because fat-free cookies, cheese, chips, and crackers were missing the critical fat that makes us feel full, we ate double — sometimes triple — the usual portion. And because manufacturers dumped extra sugar into these foods to make them taste better, we took in just as many calories and often many more. “The low-fat message backfired,” says Frank Hu, MD, PhD, a professor of nutrition and epidemiology at the Harvard School of Public Health. “It led to a proliferation of products that were loaded with sugar, refined carbohydrates, and calories.”

These days, advice about fat has shifted away from “Eat less fat” to “Eat the right fats.” Fats are now labeled “good” and “bad.” The good guys are unsaturated fats: monounsaturateds (MUFAs), found in foods like olive oil and avocados, and polyunsaturateds (PUFAs), found in sunflower and corn oils, among others, and in the omega-3s in salmon and walnuts. Both types earned gold stars because they’ve been shown to lower blood cholesterol and the risk for heart disease.