Hypothalamic and nutritional obesities in mice. A comparative study of growth and body composition

Obesities induced in mice by a single injection of gold thioglucose or by a change to a fat-enriched diet(containing 8% fat) were studied in young and adult mice of Charles River strain. These two forms of obesity were compared and contrasted with normal animals maintained on 2.5% fat diet for life. The comparison was based on individual growth, age-realted fat, water and defatted dry weight of carcasses and their distribution of weights within larger populations. Young animals on diets containing 8% fat showed an elevated accumulation of fat but not of water. Individual variations lead to an abnormally distributed population where in some animals the excess in weight was characterized by an excessive fat and lean body mass and in others by an excess fat only. Some animals showed no excessive weight when compared to animals maintained on 2.5% fat. The rapid gain in weight which followed a successful injection with gold thioglucose showed a normal distrubution and was correlated with an accumulation of fat in young and adult animals. A significant retention of water was observed only in adults. The relative merits of these obesities as models for human regulatory obesities are briefly discussed.