Effect of meal macronutrient and energy content on human performance

The effects of planned meals, varying in carbohydrate (CHO), fat and caloric content, on psychomotor performance by male subjects with unrestricted access to commercially-available foods was investigated in two residential studies. In the first study, two groups of three subjects (n = 6) completed psychomotor tasks before and after consuming a lunch consisting of 431 or 844 kcal, with caloric differences produced through covert changes in either fat or CHO content. The effects of each of four lunch conditions (low-fat, high-fat, low-CHO, high-CHO) were determined for three consecutive days. In the second study, two groups of three subjects (n = 6) received breakfast, lunch and an afternoon snack and completed psychomotor tasks after breakfast and lunch. Cumulative caloric content of the three eating occasions was approximately 700, 1200 or 1700 kcal (low, medium or high), again with differences resulting from covert changes primarily in either fat or CHO content. The effects of each of six food conditions were determined for two consecutive days. While changes in some aspects of performance were altered after meals, the effects were not related to the CHO, fat or caloric content of the meal. When subjects have unrestricted access to commercially-available foods, neither calories nor the relative fat or CHO content of normal meals influence human psychomotor task performance.