What is the effect of weight change during adulthood on a women's risk for breast cancer?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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Attained weight and weight change in adults provides the most sensitive measures of the balance between long-term energy intake and expenditure. The inverse relation between body weight (typically used as BMI) and incidence of premenopausal breast cancer has been consistently seen as summarized in a systematic review and meta-analysis of both case-control and cohort studies. [58] Heavier premenopausal women, even at the upper limits of what are considered to be healthy weights, have more irregular menstrual cycles and increased rates of anovulatory infertility, suggesting that their lower risk may be due to fewer ovulatory cycles and less exposure to ovarian hormones. Increased rates of menstrual irregularity and anovulatory infertility are also seen among very lean women, but such women are uncommon in Western populations.

In both case-control and prospective studies conducted in Western countries, the association between BMI and risk of breast cancer among postmenopausal breast cancer has been weakly positive. [58] The reduction in breast cancer risk associated with being overweight in early adult life is strongly inverse during premenopausal years and appears to persist throughout later life, thus attenuating the effect of postmenopausal adiposity. Thus, an elevated BMI in a postmenopausal woman represents two opposing risks: a protective effect due to the correlation between early weight and postmenopausal weight and an adverse effect due to elevated estrogens after menopause.

For this reason, weight gain from early adult life to after menopause should be more strongly related to postmenopausal breast cancer risk than attained weight. Weight gain and risk of postmenopausal breast cancer has been consistently supported by both case-control and prospective studies. [76] The adverse effect of excessive weight or weight gain on risk of postmenopausal breast cancer is also obscured by the use of postmenopausal hormones. Thus, to quantify the impact of weight or weight gain on postmenopausal breast cancer risk, an analysis should be limited to women who have never used postmenopausal hormones.

Among women who never used postmenopausal hormones in the Nurses' Health Study, those who gained 25 or more kg after age 18 years had double the risk of breast cancer compared with women who maintained their weight within 2 kg.

Updated data from the Nurses’ Health Study shows that weight loss that is sustained is directly related to reduced risk of breast cancer, particularly when focusing on the interval after menopause. [76] These results highlight the temporal relation between adiposity and risk, and the benefits of weight reduction among postmenopausal women.

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