The Effect of Fat-Enriched Diet on the Incidence of Spontaneous Mammary Tumors in Obese Mice

SummaryC3H/HeJ mice show a high incidence of spontaneously occurring mammary tumors. Mice made experimentally obese were observed to have an earlier appearance and a greater incidence of tumors than were the normal-weight mice. A fatenriched diet increased the observed tumor incidence in normal-weight mice to about that of obese mice given a regular diet, while a fat-enriched diet further enhanced the already augmented observed yield of mammary tumors in the obese mice given a regular diet. Statistical analysis supported the dependence of tumor incidence and appearance time on the type of diet. The calories consumed by normal mice on a fat-enriched diet was considerably below that of obese mice on a regular diet, yet produced about the same tumor incidence. A specific effect of the fat-enriched diet is suggested.High caloric diets, particularly those modified to include a high portion of fat, have been reported to promote or enhance the occurrence of several types of tumors in various species of animals (...