Long-term effects of early nutritional experience on the development of obesity in the rat

Adjustment of litter size was used to provide two levels of early nutrition to rat pups and thereby to produce adult rats of markedly different body weights. Effects of the two levels of early nutrition on adipose tissue were compared after the rats had been fed ad libitum for nearly 1 year. Mean fat cell size did not differ between rats raised in large and small litters regardless of whether they had been maintained continuously on a stock diet (upon which rats usually have normal size fat cells) or had been switched to a high-fat diet (upon which rats usually have greatly enlarged fat cells). However, rats raised in large litters had less body fat and fewer fat cells than rats reared in small litters, both in absolute terms and relative to body weight. Litter size also affected the absolute, but not relative, increase in body fat and fat cell number induced by high fat feeding. Early nutrition thus has a sustained effect on fat mass and fat cell number, but not on fat cell size, which is apparent even when adipose tissue has been induced to major alteration by the feeding of a high fat diet.