All subjects were allowed to eat as much as they wanted on both diets.However, subjects were told the purpose of the study was to examine the impact of a heart-healthy diet on disease risk. Weight loss was not a stated goal of the study because the researchers wanted to eliminate subjects who were trying to lose weight. Nevertheless, the true purpose of the study was to examine the effects of the low-fat and high-fat diet on ad libitum calorie intake and body weight.

Those on the high-fat diet experienced no significant change in body weight over the entire 12-week period. By contrast, those who followed the high-fiber, low-fat diet lost an average of 7 pounds despite eating as much as they wanted for 12 weeks. A second group on the same low-fat diet also did 45 minutes of aerobic exercise 4 times per week. This group lost about 10.5 lbs during the 12-week period.1Another study, examining the relationship between body weight and diet composition in the real world, noted that Americans who eat higher carbohydrate diets are less likely to be overweight than those consuming a diet with more fat. In the words of the authors of this study, “…free-living adults in the U.S. showed that diets high in carbohydrate were both energy restrictive and nutritious and may be adopted for successful weight management.”2 What can we learn from these 2 studies?1. Diets higher in fat tend to promote excessive calorie intake because they have a high calorie density.2. The ratio of fat to carbohydrate in the diet is probably less important than the calorie density and fiber content of the diet when it comes to feeling fuller on fewer calories.3. Diets higher in fat generally have more saturated fat and cholesterol than diets higher in carbohydrate and fiber. Bottom Line:A low-fat diet composed largely of fruits, vegetables and whole grains promotes weight loss without hunger. This is largely because such a diet will have a lower calorie density and more fiber, both of which reduce calorie intake.Such a diet would also be beneficial in helping to prevent cardiovascular disease. This is because it would have a high potassium-to-sodium ratio and be very low in saturated fat and cholesterol. A very-low-fat, more vegetarian diet has been proven to reduce ad libitum calorie intake, promote weight loss without hunger and reduce insulin resistance. All of these things improve blood lipids and reduce virtually all known risk factors for cardiovascular disease. Indeed, such a diet can often reverse atherosclerosis, hypertension and even type-2 diabetes.

By James J. Kenney, PhD, RD, LD, FACN.References:1 Arch Intern Med 2004;164:210-72 J Am Coll Nutr 2002;21:268-74