(A) Response surfaces showing the relationship between dry matter (DM) intake versus macronutrient content of the diet. Surfaces were fitted using generalized additive models (GAMs) with thin-plate splines. Three 2D slices are given to show all three nutrient dimensions (protein, P; carbohydrate, C; fat, F). For each 2D slice, the third factor is at its median (shown below the x axis in parentheses). In all surfaces, red indicates the highest value, while blue indicates the lowest value, with the colors standardized across the three slices.

(B) Relationship between protein, carbohydrate, and fat intake versus the proportion of protein, carbohydrate, and fat in the diet relative to the other macronutrients, respectively. A decelerating curve indicates regulation for a given nutrient, with the asymptote reflecting the target intake for that nutrient.

(C) Response surfaces showing the relationship between total energy intake versus macronutrient content of the diet. Energy intake was highest on low P:high F and low C:high F diets, presumably because mice overate in an attempt to achieve their protein or carbohydrate targets, with less compensatory suppression of food intake by fat.