Plasticity of fat cell number.

Rats fed ad libitum (group 1) had little change in fat cell number in epididymal depots from 6 to 27 months of age, but a marked increase in fat cell number in perirenal depots between 6 and 18 months. Food restriction of rats to 60% of group 1 from 6 weeks of age on (group 2) reduced fat cell number in both depots throughout life and prevented an increase between 6 and 18 months in perirenal depots. Food restriction of rats to 60% of group 1 from 6 weeks to 6 months of age and then feeding ad libitum (group 3) markedly reduced fat cell number in both depots at 12 months compared to group 1. However, by 18 months of age, group 3 rats had the same fat cell number as group 1 rats in both depots. Food restriction of rats to 60% of the intake of group 1 started at 6 months of age (group 4) had no effect on fat cell number in epididymal depots but prevented an increase between 6 and 18 months in perirenal fat cell number. Group 5 rats fed ad libitum but restricted in protein (same caloric intake as group 1 rats) had epididymal and perirenal depots with the same characteristics as those of group 1. These findings and others in the literature show that modifying fat cell number is a widely used means of modifying fat mass during both early and adult life.