Dietary Energy Density and Fertility: Results from the Lifestyle and Fertility Study

BACKGROUND: Diet is a modifiable lifestyle factor linked with fertility in a growing number of studies. OBJECTIVE: The objective of this study was to evaluate the association between dietary energy density (ED), a summary measure of diet quality that estimates the amount of energy per unit food (kcal/g) consumed, and conception and pregnancy outcomes. METHODS: A prospective cohort study of couples planning their first pregnancy was conducted in the Northeast region of the USA. Dietary data were collected prior to conception via 3 unannounced interviewer-administered 24-h dietary recalls. Multivariable-adjusted logistic regression (ORs and Cox proportional hazards models [RR] and 95% CIs) were estimated for continuous and categorical (tertile [T]) variables of dietary ED. RESULTS: The majority of women (n = 80; 61%) achieved clinical pregnancy. Median time to conception of a clincal pregnancy(TTC) for those who conceived was 4.64 mo with an IQR of 4.37 mo. ED modeled as a continuous variable was not associated with clinical pregnancy, live birth, or TTC after controlling for race, physical activity, and male partner's ED. When ED was categorized to consider nonlinear associations, 60%, 73%, and 50% of the participants in the tertiles (from lowest ED to highest) achieved clinical pregnancy. In multivariable logistic analyses with the middle group as the referent (ED = 1.37–1.60), membership in the highest ED group (ED >1.60) was associated with lower odds of clinical pregnancy (OR = 0.30; 95% CI: 0.11, 0.81, P = 0.02). In Cox proportional hazards analyses, membership in the highest ED group was associated with significantly longer TTC compared with the middle category (HR = 0.41; 95% CI: 0.21,0.82, P = 0.01). CONCLUSIONS: These results suggest that high dietary ED is associated with reduced fertility. This study evaluated associations between dietary energy density and the probability of conceiving clinical pregnancy, having a live birth, and the time to conception among couples planning pregnancy.