Obesity is widely accepted to be a problem of energy balance. Recent analyses have strongly suggested that the major driver of the obesity epidemic is overconsumption of energy rather than lowered energy expenditure. The carbohydrate-insulin model (CIM) of obesity is a popular model suggesting that elevated insulin secretion stimulated by a high carbohydrate diet drives this overconsumption. This model predicts fasting and postprandial insulin increase in relation to dietary carbohydrate content, which leads to higher food intake and lower energy expenditure, and the resultant positive energy balance leads to overall body weight gain.
In this study, we tested these predictions of the CIM in mice. We manipulated the diets by fixing the fat or protein content and altering the carbohydrate content, and performed two experiments. In experiment one, we measured acute postprandial insulin levels of mice following exposure to experimental diets. In experiment two, energy intake, body mass, body composition, energy expenditure, fasting blood glucose and insulin levels were all measured.
In line with the CIM, postprandial insulin levels were elevated in positive correlation with the dietary carbohydrate though not significant. Yet fasting insulin levels, energy intake, energy expenditure and body fat mass and overall body weight of mice did not follow the predicted trends by the CIM.
We conclude the CIM does not explain the impacts of macronutrients on body weight and adiposity of mice.