The long-term influence of caloric restriction during the early postweaning period on tumor prevalence in later life was investigated in the rat. Large populations of animals were maintained on 3 dietary regimens: ad libitum throughout life, restricted intake throughout post-weaning life, and restricted intake for 7 weeks immediately after weaning followed by ad libitum feeding for the remainder of life. Tumor data were analyzed by actuarial methods and are presented in terms of age-specific incidence rates and relative tumor risk values. A period of restriction in food intake, even though followed by the ad libitum regimen which is normally conducive to a relatively high incidence of neoplasms,substantially reduced tumor risk. The extent of reduction, depending on tumor type, varied from 14–83%. Of the 25 taxonomic tumor types, miscellaneous malignant tumors and all tumors of hematopoietic and lymphoreticular tissues were least affected by a limited period of dietary restriction, by contrast, the risk of benign connective-tissue tumors and tumors of epithelial tissue, particularly adenomas of the endocrine organs, was markedly reduced by the early dietary restriction. Since early restriction in food intake permanently influenced the growth pattern of these rats, the relationship between body weight and tumor risk among the 3 dietary groups was also examined. Within each group, the incidence of every tumor form was consistently greater in heavier rats than in lighter ratsi among dietary groups, however, no uniform correlation was found. Except for papillomas of the bladder, in which the risk was directly related to body weight at maturity, the reduced risk of all other tumors appears to be attributable to the influence of the dietary regimen during early life.
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Ross et al. (1971) studied this question.