An alarmingly low number of children meet public health guidelines for physical activity and dietary behaviours and, therefore, are at increased risk of developing lifestyle-related diseases. This paper describes the protocol of the B-Challenged project, which aims to co-create systemic actions to promote active outdoor play and healthy dietary behaviours before, during or after their outdoor play together with children themselves.

In five European countries, child-centred Participatory Action Research (PAR)—combined with systems dynamics methods—was conducted with 15–20 child co-researchers (aged 9–12 years) and 15–20 adult actors (eg, youth workers, local policy makers). In the first phase, the main drivers of children’s active outdoor play and related dietary behaviours were mapped by (1) analysing existing cohort data, and (2) conducting child-centred PAR. In the second phase, systemic actions targeting the local physical and social environments will be co-created and implemented by child co-researchers and adult actors to promote children’s active outdoor play and related healthy dietary behaviours. A mixed-methods design will be used to evaluate (1) if actions positively contributed to systems change and 6- to 12-year-olds’ outdoor play and related dietary behaviours (140 children per country); (2) the process of conducting multi-actor, child-centred PAR and implementing the co-created actions and (3) if the child-centred PAR positively contributed to child co-researchers’ feelings of empowerment.

Ethics approval for the mapping phase was obtained and approval for implementation and evaluation will be obtained from the five local research institutions. Participating children, one of their parents/caregivers and adult actors had given informed consent before participating in the project. Throughout the project, child-friendly methods, materials and language will be applied, and ethical challenges and potential solutions will be discussed. Project results will be disseminated locally and internationally through various channels and activities among the scientific community, professionals—for example, in health and policy making, children and other citizens.

NCT07136376.

Metabolic bariatric surgery (MBS) can lead to substantial fat-free mass loss (FFML) due to malnutrition, decreased protein intake and insufficient physical activity. Disproportional FFML has been associated with an increased risk for adverse health outcomes. Resistance training (RT) combined with protein intake contributes to maintenance and increase of fat-free mass (FFM) in healthy individuals. However, it is unclear whether RT and protein supplementation can prevent FFML after MBS.

In the EffectiveNess of pRotein supplementatIon Combined witH resistance Exercise training to counteract Disproportional fat-free mass loss following metabolic bariatric surgery (ENRICHED) randomised controlled trial, 400 patients scheduled to undergo MBS will be randomised in a 1:1 ratio to the ENRICHED perioperative care programme (intervention group) or the standard perioperative care programme of the Dutch Obesity Clinic (control group). The study is currently recruiting participants at two centres in the Netherlands: Nieuwegein and Amsterdam. The postoperative standard programme consists of 13 group sessions spread over a period of 18 months. As part of the ENRICHED programme, RT and protein supplementation will be added 3 weeks after MBS. Additional whole-body RT consists of home-based training sessions two to three times a week, and supervised RT sessions of 45–60 min once weekly, performed at 60–75% of one-repetition maximum (1-RM). Protein supplementation will start by adding 20 g of whey protein to the daily intake. The supplementation will be gradually increased with 20 g every 4 weeks until a total of 60 g whey protein a day is reached. After 12 weeks of protein supplementation, the focus shifts towards incorporating protein-rich food products into the daily dietary intake. The primary endpoint is the prevalence of disproportional FFM loss, defined as FFML/total weight loss ≥30%, at 3 months post-MBS. Secondary endpoints are differences in body composition, muscle strength and function, cardiorespiratory fitness, (cardio)metabolic health, health-related quality of life, gastrointestinal discomfort, cost-effectiveness of the intervention and treatment satisfaction. Outcomes will be assessed preoperatively and at 3, 6 and 12 months postoperatively.

The study protocol V.2.0 was approved by the Medical Research Ethics Committee Oost-Nederland (NL-OMON57119) on 9 April 2025. All participants will provide written informed consent prior to enrolment. Study findings will be disseminated through peer-reviewed publications and conference presentations. Insights gained in this study will provide evidence for a patient-tailored intervention that could be implemented in clinical practice.

NCT07156552.