A system and method for treating an animal subject having predetermined body tissues characterized by abnormal or impaired dietary fuel processing capabilities. A dietary fuel of preselected type and quantity is administered to the subject to produce in the blood supply to these body tissues a substantially elevated carbohydrate concentration during a time period following such administration. During at least a portion of the time period of such elevated carbohydrate concentration, insulin is injected into the subject in accordance with a prearranged insulin concentration versus time function. This function is independent of the magnitude of the carbohydrate concentration in the blood stream, i.e. the carbohydrate concentration does not have to be measured since it is not used to control the insulin injection. The insulin injection function produces a rapid increase in the free insulin concentration in the blood supply to the involved body tissues and is preferably a prearranged series of spaced insulin pulses that produce a series of peaks in the free insulin concentration in the blood supply to the target tissues and a continuously rising interpeak value of free insulin concentration. The coincidence of the elevated carbohydrate concentration and rapid increase in free insulin concentration thereby produces a functional improvement in the dietary fuel processing capabilities of the involved body tissues. A computer controlled insulin pumping system functions under program control to provide the series of insulin pulses.