The Search for Optimal Macronutrient Recommendations

Abstract

RDAs are essential for evaluating the quality of food intake as well as for planning food supply. Commenced in the 1950s, the ‘Seven Countries Study’ conducted by Ancel Keys gave rise to the general RDA to reduce the proportion of saturated fat in the daily diet. As a consequence, for at least two decades, all RDA committees reduced their fat recommendations from about 40 En% to levels as low as 25 En%, emphasizing in particular the reduction of saturated fat. With some time lag, the food industry followed the advice of nutritional scientists and created in nearly all product sectors low-fat alternatives with similar taste patterns to the products they replaced. However, these changes failed to influence the increasing rise of obesity worldwide. The so-called ‘American Paradox’ was born: A decrease in fat intake and a simultaneous increase in sugar intake were observed, but the increase in the prevalence of obesity was not arrested. This chapter examines the roles of the macronutrients fat, carbohydrate and protein in the diet and their respective and combined influences on weight change. It concludes that only RCTs under ad libitum conditions are valid for making judgements about the importance of the macronutrient composition of the diet in relation to energy intake and weight change, and that the world must rise to the challenge of increasing the nutrient quality of existing diets while simultaneously reducing their energy density at reasonable cost.