Long-term diet quality is associated with lower obesity risk in young African American women with normal BMI at baseline.

The prevalence of obesity [body mass index (BMI) ≥30 kg/m2] is high among African American women, with most weight gain occurring before middle age. We assessed diet quality, as measured by the Alternate Healthy Eating Index-2010 (AHEI-2010) and the Dietary Approaches to Stop Hypertension (DASH) diet score in relation to incident obesity in the Black Women's Health Study. Prospective data were collected via biennial questionnaires from 1995 to 2011. AHEI-2010 and DASH scores were calculated from food-frequency questionnaire data collected in 1995 and 2001. We restricted the analysis to 19,885 nonobese women aged 21-39 y at baseline. Multivariable Cox regression was used to estimate HRs and 95% CIs. Among women with consistent diet scores in 1995 and 2001, higher diet quality scores were inversely associated with obesity incidence: the multivariable HRs comparing highest with lowest quintiles of the AHEI-2010 and DASH scores were 0.76 (95% CI: 0.58, 0.98) and 0.68 (95% CI: 0.53, 0.88), respectively, among women with a BMI in the normal range (18.5-24.9 kg/m2) at baseline. There were no significant associations among women who were overweight at baseline. The findings suggest that a high-quality diet that is sustained over time is associated with reduced obesity risk among young African American women with a normal BMI at baseline.