Feeding in infancy, adipose tissue cellularity and obesity.
Female Sprague-Dawley rats were raised in litters of four (L4), nine (L9) and 24 (L24). The well nourished L4 rats grew insignificantly larger, heavier and fatter than the L9 controls; the underfed L24 rats remained small and stunted, and had absolutely and relatively less adipose tissue than the L4 and L9 rats. Approximately half of the rats of these three groups were fed a high-fat diet from age 18 to 43 weeks. Almost all of the rats in the fat-fed groups became obese. The amount of adipose tissue expressed as percent body weight was essentially the same in all three fat-fed groups, with the greatest relative enlargement of fat stores and increase in fat cell number in the 24-litter rats. The results show that the feeding pattern during adult life is of greater importance than early feeding experiences. The literature regarding overfeeding and underfeeding during early life is reviewed; it confirms that early overfeeding does not predispose to obesity in later life and that early underfeeding does not prevent or diminish the development of nutritional obesity and adipose tissue hypercellularity. Early underfeeding seems to affect more the regulation of the feeding behavior than the intrinsic functions and growth potential of adipose tissue; it may even stimulate the development of obesity.