Using the MRC framework for complex interventions to develop a childhood obesity prevention trial: the baby milk trial

Objective Obesity is common even in young preschool children. In England by the time children start school, more than 1 in 5 are overweight or obese. Infancy is a period of rapid growth, and there is evidence for long-term ‘programming effects’ of rapid weight gain and nutrition during infancy. We describe the development of a complex behavioural intervention to avoid rapid infancy weight gain and prevent childhood obesity. Methods We reviewed the literature on early life risk factors and the role of infant nutrition and weight gain in programming later obesity. We undertook systematic reviews to understand parents9 experiences of bottle-feeding and the determinants of early weaning. We conducted qualitative studies with mothers and healthcare professionals using an iterative process to develop and refine the intervention. Finally, we developed a questionnaire to understand how the intervention works and set up an explanatory randomised controlled trial to evaluate the cost-effectiveness of the intervention. Results Our systematic review on parents9 experiences of bottle feeding (23 studies) found that mothers who bottle-fed their babies experienced negative emotions such as guilt, anger and worry. They received little information from healthcare providers, resulting in mistakes being made in feed preparation. Our systematic review on determinants of early weaning (60 studies) found strong evidence for six determinants (maternal age, socio-economic status, education, smoking, not breastfeeding and lack of information or advice from healthcare providers), but a paucity of studies on psychosocial determinants. Our qualitative studies found that parents often interpret ‘demand feeding’ as meaning feeding in response to crying and increasing the volume of feeds if the baby finished the bottle. Our 57-item questionnaire to assess maternal attitudes and feeding practices showed good reliability, and reasonable validity and internal consistency. The resulting intervention targets multiple infant feeding behaviours, is informed by Social Cognitive Theory and consists of Motivational, Action Planning and Coping Planning components. Conclusion In addition to developing our specific intervention and evaluation materials, use of the MRC Framework has helped to build a generalisable evidence base for early life nutritional interventions. In particular, these studies highlighted the lack of support perceived by mothers who formula-feed.