Low Fat - Popular Diets: Obesity

Content provided by the Faculty of the Harvard Medical School

Low fat

Books: Eat More, Weigh Less; The Pritikin Principle

Once the main strategy for losing weight, low-fat diets have been shoved aside by the low-carb frenzy. That's not necessarily a bad thing, since neither of the two foundations on which low-fat diets were built — fat makes you fat, and fat is bad for the heart — are very solid. Healthy fats can actually promote weight loss, while some fats are good for the heart and eliminating them from the diet can cause problems.

Rationale. Scores of low-fat diets have been promoted over the years. One of the best known is Dr. Dean Ornish's "Eat More, Weigh Less" plan, which grew out of the cholesterol hypothesis developed in the 1960s and '70s. First, the idea was to cut cholesterol from the diet, because it contributed to heart disease. Then researchers realized that dietary fat has an even bigger influence on heart disease, which spurred the low-fat diet. Dr. Ornish's diet originally focused on preventing heart disease but has switched to emphasize weight loss.

Since fat contains 9 calories per gram while carbohydrates contain 4, you can theoretically double your food intake without taking in more calories by cutting back on fatty foods and eating more that are full of carbohydrates, especially water-rich fruits and vegetables.

Keep in mind that the Ornish plan doesn't stop at a whole-grain, vegetarian, very low-fat (less than 10% of calories from fat) diet, but also includes exercise, stress management, and group support. The related Pritikin Principle (which also first originated in the 1970s) also limits dietary fat to 10% of calories and is largely based on vegetables, grains, and fruit.

Bottom line. Low-fat diets have unquestionably helped some people lose weight and keep it off. They've been dismal failures for others, in part because they tend to be less filling, less flavorful, and all around less satisfying than other eating strategies. They also tend to be fairly restrictive about food choices, which can limit your options when dining out.

Last updated:	June 20, 2007