Response of mammary tumors to caloric restriction for different time periods during the promotion phase.

Rats treated with 7,12-dimethylbenz[a]anthracene were subjected to 25% caloric restriction for varying times during the promotion/progression phase of mammary tumorigenesis. Caloric restriction was inhibitory to a statistically significant extent when it was maintained for the entire four-month study or only during the first or last two months. Restriction for the first month with subsequent ad libitum feeding led to rapid weight gain with concomitant appearance of tumors. These data indicate that caloric restriction can be instituted late in the tumorigenic process with an acute response of tumor growth to caloric intake or body weight.