Low Fat Diets & Popular Diets

Popular diets range in nutrition composition from low fat, low carbohydrate to high fat, high protein and a whole range in-between. The question is, what works and what is the association of health and nutrition on these diets? In response to the growing epidemic of obesity worldwide, The U.S. Department of Agriculture (USDA) has begun a research program to attempt to answer those questions.

In the April 2001 issue of The Journal of the American Dietetic Association, the first two parts of the first phase of this project were reported.  This report includes the analysis of the existing information about popular diets and a review of the literature on the subject. 
The outcome?

  1. Body mass index (an indication of body fatness) tended to be lower for men and women on high carbohydrate, lower fat diets, and highest for those on low carbohydrate diets.

  2. Energy intake (calories consumed) was lowest for people following a vegetarian diet.

  3. Diet quality, as measured by the healthy eating index (HEI) was highest for people eating high carbohydrate diets, and lowest for people eating low carbohydrate diets.

The study analyzed the food intake of 10,014 adults in the United States over three years – 1994, 1995, and 1996, and included people who were on weight reduction diets and those who were not.

Diets Defined

What is a low carbohydrate diet? These are diets that have 20% or less of the calories coming from carbohydrate sources. So, if you were eating 2000 Calories a day, only 400 of those calories (about 100 grams) could come from carbohydrates. Low carbohydrate diets include the Atkins diet, and other high protein or high fat diets. While weight loss occurs on these types of diets when the calories are reduced, this type of eating (low carbohydrate) is associated with the highest body fat in men and women. 

Very low fat diets are those that have 10% of less of the calories from fat. The most popular diets of this type are the Ornish diet and the Pritikin diet. Although these diets are not necessarily vegetarian, you really can’t eat too many animal foods and still have a very low fat diet, so animal foods are quite limited on these diets.

Moderate fat, high carbohydrate diets are those in which the fat is below 30% of calories, and the carbohydrate is 55% or more. Many popular weight reduction plans are of this type, and your personal diet plan fitsbest into this category. The good news is that this is the type of diet that is associated with a lower body mass index, which is the goal for weight loss.

Diet Quality

For good nutrition and good health, eating a lower fat, higher carbohydrate diet is not enough. The USDA study looked at high carbohydrate eating patterns that consisted of “Pyramid” versus “non-Pyramid” types of eating. The difference is that a Pyramid style of eating attempts to include at least one serving of each food group in the Food Guide Pyramid (fruits, vegetables, grains, low-fat dairy, low-fat meats and meat alternatives). 

When compared to a non-Pyramid diet, the Pyramid type of higher carbohydrate diet was higher in nutritional quality and lower in sugar. Of course, this makes sense. When you eat more carbohydrates in the form of whole grains, vegetables, and fruits, your diet will be of higher quality.

Some Conclusions  

In reviewing the literature on diet, the USDA researchers found a lot of erroneous information, no surprise!

  • One of the things they found was that there was no evidence to suggest that low-carbohydrate diets have any metabolic advantage for weight loss.
  • The other conclusion, which makes sense, is that the composition of the diet is not really an important factor in weight loss, only the reduction in calories is important.
  • Lastly, the results of their extensive research so far indicate that the optimal diet for weight maintenance is one that controls fat intake – your personal diet is designed to do just that.


There are many limitations to what is known about diets at this time. Most studies have very small groups of subjects, and there are very few studies that show the long-term effects of different diets. However, current evidence suggests that a healthy, lower fat way of eating, one that includes a variety of vegetables, grains, fruits, low fat animal foods or meat alternatives is the way to go for long term weight maintenance and for good health. Low fat diets really do work!