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 (kcal) or kilojoules (kJ)] intake to food weight (grams, g) 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 (WHI). DESIGN: Prospective cohort study of clinical trial and observational study participants. PARTICIPANTS/SETTING: Postmenopausal women ages 50–79 years (n = 92,295) enrolled in the observational study or the calcium and vitamin D trial and hormone replacement therapy trials. MAIN OUTCOME MEASURES: Incident, medical record-adjudicated, obesity-related cancers during follow-up. Exposure variable was DED (kcal/g for the total diet) from self-reported dietary intake at baseline using a food frequency questionnaire. STATISTICAL ANALYSES PERFORMED: 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 (BMI)-stratified models were generated to investigate BMI as a potential modifying factor. RESULTS: DED was associated with higher BMI (mean ± standard deviation: 28.9 ± 6.0 versus 26.3 ± 4.9 kg/m(2)) and waist circumference (89.3 ± 14.2 versus 82.4 ± 12.4 cm) for DED quintiles 5 versus 1, respectively. DED was associated with a 10% increased risk of any obesity-related cancer (subhazard ratio(Q5 vs Q1): 1.1; 95% confidence interval, 1.03–1.2; 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 intervention to reduce obesity-associated cancer risk.