Table 1 Application and adaptation to the PRALIMAP trial of the intervention dose determination framework

Intervention periods identification

2 intervention periods = intervention implemented during the grade 10 and 11 school years

Identification and categorisation of the programme actors

Supervisors: PRALIMAP monitors

Anchor personnel: school professionals (administration staff, teachers, catering professionals, school nurses, …)

Targets: high school students

Indicator development

Non-programme-driven activities indicators:

* Developed for the 72 IRG

* Concerned respectively the educational nutritional, screening and environmental activities performed independently of the PRALIMAP trial

Programme-driven activities indicators:

* Developed for the 36 IRG-A

* Concerned the PRALIMAP activities planned by the frame of reference:

- 12 IRG-Education: indicators investigated the delivery of lectures and collective works on nutrition and the participation in PRALIMAP meetings

-12 IRG-Screening, indicators investigated the delivery of weight and height data and of the proposition to participate to adapted overweight care management and the participation of students in group educational sessions

- 12 IRG-Environmental, indicators investigated the delivery of high school environment improvements (adapted food and physical activity availability) and participation in PRALIMAP parties

Data collection

Data collected before the programme implementation:

* High schools nutritional environment (ex: water drinking fountain, proposed physical activities …) : nutritional surveys participated in by school staff

* Nutritional behaviours : adolescent self-administered questionnaires and anthropometric measures

Data collected during implementation:

* Activities delivery data: activity reports, pupil satisfaction surveys (care management, PRALIMAP meeting…)

* Appreciation of PRALIMAP trial : self administered questionnaire

* Evolution of the offer of school catering and physical activity free equipment and the nutritional environment close by the high school: nutritional surveys participated in by school staff

Data collectedat the end of the programme:

* Activities delivery, school staff and teenagers’ participation and favouring and limiting factors :

- focus group of staff responsible for interventional strategies (high school professionals, head teachers)

- individual semi-structured interview of the PRALIMAP monitors

- focus group of health professionals intervening with overweight and obese adolescents in high school screening

- nutritional survey of high school professionals and students

Data analysis and evaluation of indicators

Indicator report sheets are elaborated for every IRG including:

* Quantitative indicators expressed in the form of mean or percentage (eg : pupils' activity participation rate)

* Qualitative (literal) indicators (eg : ranges of food proposed in the lunches, delivery or not of activity)

The number of indicator report sheets varied from 3 to 6 according to the high school assigned strategies (Table 3) :

*IRG–Education : 1 indicator report sheet of non-programme-driven activities + 1 indicator report sheet of programme-driven activities

*IRG–Education control : 1 indicator report sheet of non-programme-driven activities

*IRG– Screening : 1 indicator report sheet of non-programme-driven activities + 1 indicator report sheet of programme-driven activities

*IRG–Screening control : 1 indicator report sheet of non-programme-driven activities

*IRG–Environment : 1 indicator report sheet of non-programme-driven activities + 1 indicator report sheet of programme-driven activities

*IRG–Environment control : 1 indicator report sheet of non-programme-driven activities

Score assignment

Number of experts:18 (3 groups of 6)

Type and specialty of experts: researchers, field professionals or decision-makers, specialists in diet, physical activity and\or evaluation, knowing or not the PRALIMAP trial, practicing or not in Lorraine Region

IRG assigned between the experts: the IRG were fairly and anonymously distributed among the experts

Individual scoring aid: IT (Excel®)

Scoring : ranging from 0 to 20 for every period, domain and characteristic in each IRG

Threshold defined for the standard deviation and/or the range: if a standard deviation was higher than 2.5 or a range higher than 6 was observed, the experts debated and proposed a new notation; discrepant scores were then preserved.

Taking into account between-group variability: A fictitious high school was created and scored by the 3 groups

Intervention dose calculation

Application of intervention dose formula to assigned scores: Dose = DQt x (mean (DQl, PQt, PQl)/20)

A group effect has been evidenced thanks to the fictitious high school and required score adjustment varying from 0.8 to 2.8 points.

Eventually 216 doses (108 per period) were calculated (Table 3).