Plasma insulin and the time pattern of feeding in the rat

Blood levels of glucose and insulin during meals and between-meal-intervals were measured in virtually undisturbed rats. After a peak due to glucose absorbed from the meal blood sugar soon reverts to the pre-meal level. Insulin shows a similar peak followed by a continuing decline so that just before the next meal it is lower than at any other time. In terms of the glucostatic theory this might mean that meals are triggered by a critical drop of insulin. However, intravenous infusions of glucose, resulting in continuously high insulin, do not affect timing or size or meals. Glucostatic factors probably are of minor importance in meal-to-meal regulation in the rat. However, they may subserve nutritional homeostasis on at least two other points.