Technical Abstract: The USDA has issued the Food Guide Pyramid (FGP) to help Americans choose healthy diets. We examined whether adherence to the 1992 and 2005 FGP was associated with moderate energy and adequate nutrient intakes. We used data for 2138 men and 2213 women, aged >18y, from the 2001-02 US National Health and Nutrition Examination Survey. Quadratic programming was used to generate diets with minimal departure from current dietary practices, while meeting specified constraints. We examined the effect of # servings/d of Food Pyramid groups set at 1992 and at 2005 FGP recommendations for 1600, 2200, and 2800 kcal levels. We calculated energy and nutrients provided by different FGP dietary patterns. With the current US dietary practices, the 1992 FGP, without sodium restriction, is likely to permit approximately 200 more kcal intake than recommended for all of three energy level patterns. Although it can meet most of old nutrient recommendations (1989), it fails to meet the latest dietary reference intakes, especially for the 1,600 kcal level. The 2005 FGP appears to provide less energy and more adequate nutrient intakes, with the exception of vitamin E and potassium for some groups. However, without discretionary calorie restriction, Americans are at risk of having excessive energy intake even if they follow the 2005 FGP food serving recommendations. Our analysis suggests that following the 2005 FGP may be associated with lower energy and optimal nutrient intake. Careful restriction of discretionary calories appears necessary for appropriate energy intakes to be maintained.