Association between Dietary Energy Density and Obesity-Associated Cancer: Results from the Women's Health Initiative

Background: Dietary energy density (DED) is the ratio of energy (kilocalories or kilojoules) intake to food weight (grams) and is a measure of diet quality. Consumption of foods high in DED has been associated with weight gain in adults. Objective: To investigate the association between baseline DED and incident obesity-associated cancers in the Women's Health Initiative. Design: Prospective cohort study of clinical trial and observational study participants. Participants/setting: Postmenopausal women aged 50 to 79 years (N=92,295) enrolled in the observational study or the calcium and vitamin D trial and hormone replacement therapy trials of the Women's Health Initiative. Main outcome measures: Incident, medical record-adjudicated, obesity-related cancers during follow-up. Exposure variable was DED (kilocalories per gram for the total diet) from self-reported dietary intake at baseline using a food frequency questionnaire. Statistical analyses: The associations between DED and each incident cancer, or any obesity-related cancer, were examined using competing-risks regression models, with death as a competing risk. Body mass index-stratified models were generated to investigate body mass index as a potential modifying factor. Results: DED was associated with higher body mass index (28.9±6.0 vs 26.3±4.9) and waist circumference (89.3±14.2 vs 82.4±12.4 cm) for DED quintiles 5 vs 1, respectively. DED was associated with a 10% increased risk of any obesity-related cancer (subhazard ratio_{Q5 vs Q1}: 1.1, 95% CI 1.03 to 1.2; P=0.004). This increased risk appeared limited to women who were normal weight at enrollment. Conclusions: Higher DED may be a contributing factor for obesity-related cancers, especially among normal-weight postmenopausal women and, as such, could serve as a modifiable behavior for dietary interventions to reduce obesity-associated cancer risk.