Figure 4.

Regulation of feeding rate by dietary nutrient concentration. (A) Food intake over 24 hours on radiolabeled medium (average ± s.d.). Consumption is reduced with increasing levels of sucrose and yeast extract (S and Y, respectively, all shown as w/v), except at the highest concentration of sucrose (20%), where the effect of yeast is muted. All pairwise comparisons are significantly different (p < 0.001, one-way ANOVA followed by Tukey post-hoc test) except between the three diets with 20% sucrose (p > 0.05). (B) Relationship between food intake volume and macronutrient content of the diet. The size and darkness of the circles are scaled with increasing food intake. In general, increasing the concentration of dietary protein or carbohydrate reduces intake. However, conditions can be found where a change in the concentration of a single nutrient does not trigger compensatory feeding. (C) Consumption shows a strong negative correlation with caloric value of the diet, best described by a power model, suggesting an inverse relationship between the two parameters (y = m/x^b; m = 0.40, b = 1.39). The power fit and R² value are shown. When b = 1, the product of food intake and dietary caloric content is a constant, m, which describes a daily caloric intake target. When b > 1, over-feeding occurs as the caloric value of the diet decreases. The non-linear relationship between food intake and dietary caloric content was also tested using Spearman’s correlation coefficient and confirmed a strong negative correlation (r = −0.90, p = 0.005). All results are for Canton-S males.