State-space models of insulin and glucose responses to diets of varying nutrient content in men and women.

Discrete-time state-space models were developed to describe contemporaneous responses of plasma insulin and glucose of normal human subjects. Male and female subjects ingested three consecutive identical meals from isocaloric diets classified as high-carbohydrate, high-fat, high-protein, or standard. Distinctly different glucose and insulin responses were measured in men and women. A seven-state system of linear equations, three in insulin and four in glucose, was identified and estimated to describe responses in men. A six-state system, three in insulin and three in glucose, describes responses in women. Model simulations at 15-min intervals closely match measured concentrations over a 12-h period. Effects of diet content and meal timing on insulin and glucose concentrations were quantified. Dynamic insulin and glucose responses to isocaloric meals of pure carbohydrate, fat, and protein diets were projected on the basis of models developed from mixed diets. The symmetry of the projections indicates that positive excursions in glucose concentrations associated with carbohydrate intake may be matched with negative excursions associated with fat and protein intake to help manage postmeal glucose excursions.