BACKGROUND: In the evaluation of childhood obesity interventions, few researchers undertake a rigorous feasibility stage in which the design and procedures of the evaluation process are examined. Consequently, phase III studies often demonstrate methodological weaknesses. PURPOSE: Our aim was to conduct a feasibility trial of the evaluation of WATCH IT, a community obesity intervention for children and adolescents. We sought to determine an achievable recruitment rate; acceptability of randomisation, assessment procedures, and dropout rate; optimal outcome measures for the definitive trial; and a robust sample size calculation. METHOD: Our goal was to recruit 70 participants over 6 months, randomise them to intervention or control group, and retain participation for 12 months. Assessments were taken prior to randomisation and after 6 and 12 months. Procedures mirrored those intended for a full-scale trial, but multiple measures of similar outcomes were included as a means to determine those most appropriate for future research. Acceptability of the research and impact of the research on the programme were ascertained through interviewing participants and staff. RESULTS: We recruited 70 participants and found that randomisation and data collection procedures were acceptable. Self-referral (via media promotion) was more effective than professional referral. Blinding of assessors was sustained to a reasonable degree, and optimal outcome measures for a full-scale trial were identified. Estimated sample size was significantly greater than sample sized reported in published trials. There was some negative impact on the existing programme as a result of the research, a lesson for designers of future trials. LIMITATIONS: We successfully recruited socially disadvantaged families, but the majority of families were of White British nationality. The composition of the participants was an added valuable lesson, suggesting that recruitment strategies to obtain a more heterogeneous ethnic sample warrant consideration in future research. CONCLUSIONS: This study provided us with confidence that we can run a phase III multi-centre trial to test the effectiveness of WATCH IT. Importantly, it was invaluable in informing the design not only of that trial but also of future evaluations of childhood obesity treatment interventions.

Original publication




Journal article


Clin Trials

Publication Date





755 - 764


Adolescent, Adult, Child, Feasibility Studies, Female, Humans, Male, Middle Aged, Obesity, Patient Selection, Research Design, Sample Size, Surveys and Questionnaires, United Kingdom