The relationship of the Diet Quality Index to prevalence of overweight in black and white adolescent girls: an examination of data from the National Heart, Lung, and Blood Institute's Growth and Health Study

The NHLBI's Growth and Health Study (NGHS) data set provided an opportunity to test differences in diet quality and its relationship to weight classification for black (n=270) and white (n=243) adolescent females. Three-day food records from adolescents enrolled in the Washington, D.C. center of the NGHS were scored according to the Diet Quality Index (DQI) developed by Ruth Patterson and others. This index stratifies food intake into three levels for scoring across eight dietary factors. A score of zero showed that the goal was met, while a score of one indicated a fair evaluation, and a score of two indicated a poor rating to create an index score ranging from zero to 16.

Statistical analysis by a t-test showed whites had significantly better DQI scores than blacks in the NGHS sample (black mean = 9.4, white = 8.1). Black females had a greater prevalence of overweight than do their white counterparts. To evaluate how dietary quality relates to the development of overweight, DQI scores were compared to body mass index measurements to note the relationship of diet quality to increasing weight for body height. No relationship was found between BMI and DQI. When the independent variables of race and body weight classification were assessed for their impact upon the dependent variable of diet quality; the influence of race proved significant while weight classification did not. This evidence suggests that practitioners must assess the current dietary status of clients prior to assuming a particular dietary pattern based upon body weight for height alone.