Low-fat diets have long been touted as the key to a healthy weight and to good health. But the evidence just isn’t there: Over the past 30 years in the U.S., the percentage of calories from fat in people’s diets has gone down, but obesity rates have skyrocketed. (1,2) Carefully conducted clinical trials have found that following a low-fat diet does not make it any easier to lose weight than following a moderate- or high-fat diet. In fact, study volunteers who follow moderate- or high-fat diets lose just as much weight, and in some studies a bit more, as those who follow low-fat diets. (3,4) And when it comes to disease prevention, low-fat diets don’t appear to offer any special benefits. (5)
Part of the problem with low-fat diets is that they are often high in carbohydrate, especially from rapidly digested sources, such as white bread and white rice. And diets high in such foods increase the risk of weight gain, diabetes, and heart disease. (See Carbohydrates and Weight, below.)
For good health, the type of fat people eat is far more important that the amount (see box), and there’s some evidence that the same may be true for weight control. (6–9) In the Nurses’ Health Study, for example, which followed 42,000 middle-age and older women for eight years, increased consumption of unhealthy fats—trans fats, especially, but also saturated fats—was linked to weight gain, but increased consumption of healthy fats—monounsaturated and polyunsaturated fat—was not