The effect of dietary carbohydrate:fat ratio on energy intake by adult women

The effect of the dietary carbohydrate:fat (C:F) ratio on the spontaneous energy intake by healthy adults was investigated by comparing a high-carbohydrate diet (fat 24%, carbohydrate 58%, protein 18% of energy) and a high-fat diet (fat 47%, carbohydrate 35%, protein 18% of energy) in a 2 × 2 week cross-over design. Subjects were 22 healthy nuns in a Trappist convent with very regular activities. The diets consisted of combinations of liquid formula (75%) and standardized snacks (25%). The difference in C:F ratio was concealed: energy density, taste and appearance were similar. Energy consumption was recorded continuously. The mean daily energy intakes remained constant: 8276 kJ (1978 kcal). The difference in mean daily energy intake between diets was 73 kJ ± 180 (SEM). Small changes in body weight were observed, but these are argued not to indicate definitive effects. It is concluded that changing the C:F ratio within commonly occurring ranges does not influence the spontaneous energy intake of healthy adults. The composition of the dietary fat was kept constant. Under practical conditions a change in the C:F ratio will also induce a change in the fatty acid composition of the diet, which might affect the energy intake regulation. Other experiments are required to see whether the C:F ratio can affect body composition or other physiological parameters in the long run.