A review of development of adipose cellularity in man and animals

Animals regulate body weight by increases or decreases in caloric intake or energy output. Obesity may be viewed as a disorder of this regulation: excess adiposity occurring through an increase in adipose cell size, cell number, or both. The number of adipocytes in the normal rat is determined by five weeks of age and is unchanged by subsequent dietary manipulations. In contrast, adipose cell size can be changed throughout the animal's life.