Some Musings About Differential Energy Metabolism With Ketogenic Diets

Ketogenic states are of 3 major types: total starvation and those resulting from the consumption of semistarvation, ketogenic diets, and eucaloric ketogenic diets. All are characterized by little or no dietary carbohydrate, resulting in a fat-based metabolism with sustained ketonemia of varying degrees in each state. The latter 2 diets are clinically useful with important impacts on both aspects of the energy balance equation with increased satiety and less hunger on the intake side and probably increased energy expenditure on the output side; both may have important implications for the successful long-term management of obesity. Consideration of older research regarding the hormonal response to carbohydrate-free dieting and recent findings on hepatic glycogen status that occurs with sustained ketonemia support the likelihood that there are profound differences in 24-hour gluconeogenesis rates between ketogenic diets and balanced diets containing substantial carbohydrate. This metabolic distinction could have a meaningful impact to increase the thermic effect of feeding and daily energy expenditure amounting to 100 kcal/d or more with each of the ketogenic diets.