Autoregulatory homestatic nature of energy balance.

This paper proposes a new theory regarding energy regulation in man. Current theory states that similar adults have similar energy requirements when engaged in similar activities. As a corollary, if activities remain constant and energy intake is altered, weight will change. This theory has been unable to explain the repeated observations that individuals of the same sex and age and engaged in similar work show a mean weekly coefficient of variation in energy intake of about 16% without significant fluctuations in body weight. Furthermore, repeated studies have failed to show any individual "pattern" relating energy intake to output. This lack of pattern has been attributed either to methodological error or to the fact that human energy requirements cannot be determined by current methods. This paper shows that neither case is correct. The explanation lies in the stochastic stationary nature of energy requirements. Because of the nature of significant intraindividual variations noted in all experiments, "requirement" is a dynamic concept, and energy balance will vary as a matter of course about zero. The implications of this for the individual, society, and policy are enormous and are discussed herein.