ABSTRACT
This chapter focuses on non-genetic factors involved in determining body weight and body composition. In most people the settling point remains constant over time. Human eating is a learned habitual behavior thought to stem from conditioning of responses based on previous experience in which the postingestive consequences of a particular food act as unconditioned stimuli. A permanent alteration in eating behavior would create a new behavioral phenotype and functional phenotype and might disrupt the steady state between intake and expenditure. There are a number of factors involved in determining the amount and composition of fuel burned by an individual. Theoretically, the metabolic phenotype can be modified at any time and such modification can affect the fate of ingested energy. The functional phenotype represents the interaction between the behavioral and metabolic phenotypes. As an individual interacts with and responds to a given environment, the functional phenotype constantly changes within the limits defined by the genotype.
