Background & aim: A diet quality index (DQI) is a tool that provides an overall score of an individual's
dietary intake when assessing compliance with food-based dietary guidelines. A number of DQIs have
emerged, albeit their associations with health-related outcomes are debated. The aim of the present
study was to assess whether adherence to dietary intervention, and the overall quality of the diet, can
predict body composition changes.
Methods: To this purpose, overweight/obese adolescents (n ¼ 117, aged: 13e16 years; 51 males, 66 females) were recruited into a multi-component (diet, physical activity and psychological support) familybased group treatment programme. We measured the adolescents' compliance and body composition at
baseline and after 2 months (intensive phase) and 13 months (extensive phase) of follow-up. Also, at
baseline, after 6 months, and at the end of follow-up we calculated the DQI.
Results: Global compliance with the dietary intervention was 37.4% during the intensive phase, and 14.3%
during the extensive phase. Physical activity compliance was 94.1% at 2-months and 34.7% at 13months
and psychological support compliance were growing over the intervention period (10.3% intensive phase
and 45.3% during extensive phase). Adolescents complying with the meal frequency criteria at the end of
the extensive phase had greater reductions in FMI z-scores than those did not complying (Cohen's
d ¼ 0.53). A statistically significant association was observed with the diet quality index. DQI-A variation
explained 98.1% of BMI z-score changes and 95.1% of FMI changes.
