Calorie Restriction Lowers Breast Cancer Risk
Study Offers Clues About the Role of Early Diet in Disease
Michels says she chose women with a history of anorexia for her study because the group represented a unique human model of extreme, prolonged calorie restriction early in life.
The researchers are not recommending anorexia as a means of preventing breast cancer. About 6% of people with severe anorexia die from their disease, according to the National Association of Anorexia Nervosa and Associated Disorders.
Researchers identified more than 7,300 women in Sweden who had been hospitalized for anorexia prior to age 40 over a three-decade period. A comprehensive national cancer registry was used to compare breast cancer frequency among the former anorexia patients to that of the population at large.
Women with a history of the eating disorder were 53% less likely to get breast cancer than the general female population.
This jumped to a 76% reduction in breast cancer risk in those women who had also given birth. Pregnancy has long been linked to reduced breast cancer risk.
Possible reasons for the observed reduction in breast cancer risk include decreased levels of estrogen and other growth hormones among women on extremely low calorie diets and the restrictive impact that such diets have on cell division.
"Very low calorie intake and low body weight are associated with low estrogen levels, and low estrogen levels have been linked to a lower risk of breast cancer," says Brigham and Women's Hospital chief of obstetrics and gynecology Robert Barbieri, MD.
Another possible reason for the association, Barbieri says, is that people on very low calorie diets have lower levels of human growth hormones such as insulin-like growth factor type 1 (IGF-1). Animal studies show that IGF-1 can promote tumor growth. Barbieri was not involved in the study.
"In worms, growth hormones have been directly linked to life expectancy, and people are wondering if this might be another way in which calorie intake could regulate cancer risk," he tells WebMD.