Effectiveness of DOiT programme
The school-based Dutch Obesity Intervention in Teenagers (DOiT) programme is an evidence-based obesity prevention programme tailored to adolescents attending the first two years of prevocational education in the Netherlands. The initial programme showed promising results during an effectiveness trial. The programme was then adapted and prepared for nationwide dissemination. To gain more insight into the process of translating evidence-based approaches into ‘real world’ (i.e. ‘natural’) conditions, our research aims were to evaluate the impact of the adapted DOiT programme on adolescents’ adiposity and energy balance-related behaviours during natural dissemination and to explore the mediating and moderating factors underlying the DOiT intervention effects.
We conducted a cluster-controlled implementation trial with 20 voluntary intervention schools (n=1002 adolescents), who adopted the programme, and 9 comparable control schools (n=484 adolescents). We measured adolescents’ body height and weight, skinfold thicknesses (i.e. triceps, biceps, suprailiac and subscapular), and waist circumference. We assessed adolescents’ dietary and physical activity behaviours by means of self-report. Data were collected at baseline and at 20-month follow-up. We used multivariable multi-level linear or logistic regression analyses to evaluate the intervention effects and to test the hypothesized behavioural mediating factors. We checked for potential effect modification by gender, ethnicity and education level.
We found no significant intervention effects on any of the measures of adiposity (BMI, waist circumference or skinfolds) or behavioural outcomes. Furthermore, we found no mediating effects by any of the hypothesized behavioural mediators. Stratified analyses for gender showed that the intervention was effective in reducing sugar-containing beverage consumption in girls (B=-188.2 ml/day; 95%CI=-344.0; -32.3). In boys, we found a significant positive intervention effect on breakfast frequency (B=0.29 days/week; 95%CI=0.01; 0.58). Stratified analyses for education level showed an adverse intervention effect (B = 0.09; 95%CI=0.02; 0.16) on BMI z-scores for adolescents attending the vocational education track.
Although not successful in changing adolescents’ adiposity, the adapted DOiT programme had some beneficial effects on specific obesity-related behaviours in subgroups. This study underlines the difficulty of translating intervention effectiveness in controlled settings to real world contexts. Adaptations to the implementation strategy are needed in order to promote implementation as intended by the teachers.