Lakshman et al. Trials (2015) 16:442 DOI 10.1186/s13063-015-0941-5
TRIALS
STUDY PROTOCOL
Open Access
Effectiveness of a behavioural intervention to prevent excessive weight gain during infancy (The Baby Milk Trial): study protocol for a randomised controlled trial Rajalakshmi Lakshman1*, Fiona Whittle1, Wendy Hardeman2, Marc Suhrcke3, Ed Wilson4, Simon Griffin1 and Ken K Ong1
Abstract Background: Infancy is a period of rapid growth and habit formation and hence could be a critical period for obesity prevention. Excess weight gain during infancy is associated with later obesity and formula-fed babies are more likely to gain excess weight compared to breastfed babies. The primary trial outcome is a change in the weight standard deviation score from birth to 1 year. Methods/Design: We will recruit 650 to 700 parents who introduce formula-milk feeds within 14 weeks of their baby's birth to a single (assessor) blind, parallel group, individually randomised controlled trial. The focus of the intervention is the caregiver (usually the mother), and the focus of the primary outcome is the infant. The intervention group will receive the behavioural intervention, which aims to reduce formula-milk intake, promote responsive feeding and healthy weaning, and prevent excessive weight gain during infancy. The intervention is based on Social Cognitive Theory and action planning (‘implementation intentions’). It consists of three components: (1) a motivational component to strengthen parents’ motivation to follow the Baby Milk feeding guidelines, (2) an action planning component to help translate motivation into action, and (3) a coping planning component to help parents deal with difficult situations. It will be delivered by trained facilitators (research nurses) over 6 months through three face-to-face contacts, two telephone contacts and written materials. The control group will have the same number of contacts with facilitators, and general issues about feeding will be discussed. Anthropometric outcomes will be measured by trained research staff, blind to group allocation, at baseline, 6 months and 12 months following standard operating procedures. Validated questionnaires will assess milk intake, temperament, appetite, sleep, maternal quality of life and maternal psychological factors. A 4-day food diary will be completed at 8 months. Discussion: The results of the trial will help to inform infant feeding guidelines and to understand the links between infant feeding, behaviour, appetite and growth. Trial registration: ISRTCN20814693. Registration date 13 January 2011. Keywords: Infancy, Formula-milk, Obesity, Weight gain, Prevention, Behavioural change, RCT
* Correspondence:
[email protected] 1 MRC Epidemiology Unit and UKCRC Centre of Excellence in Diet and Activity Research (CEDAR), University of Cambridge, Cambridge, UK Full list of author information is available at the end of the article © 2015 Lakshman et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Lakshman et al. Trials (2015) 16:442
Background Childhood obesity has important consequences for morbidity and mortality in childhood and in later life [1]. In 2010, 43 million children under the age of five were obese or overweight worldwide and the prevalence is predicted to rise from 6.7 % to 9.1 % in 2020 [2]. In England, data from the National Child Measurement Programme (NCMP) show that by the time children start school, more than one in five are overweight, and one in 10 are obese [3]. Hence, tackling childhood obesity through focussing on the early years has become a national priority [4]. However, to date, there is little evidence on which to develop effective strategies to prevent childhood obesity [5]. A Cochrane Review identified 22 randomised trials to prevent childhood obesity; although some diet and physical activity interventions were effective in promoting a healthy diet and increased physical activity levels, they were not on the whole effective in preventing weight gain [6]. Only one of the included studies recruited children below one year of age (average age 21 months, n = 43), and that was a home-visiting programme for high-risk Native-American children, focussing on improving parenting skills to develop appropriate eating and exercise behaviours to prevent obesity [7]. Infancy is a period of rapid growth and could be a critical time when obesity prevention may be most effective. Recent systematic reviews have described a consistent association between rapid weight gain in infancy and subsequent obesity risk in childhood and later life [8–10]. Energy deposition as a percentage of total energy requirements decreases from 40 % at 1 month to 1 to 2 % from 12 months until mid-adolescence. Therefore, infancy weight gain is more closely related to energy intake, than is weight gain in childhood or in later life. In 2004, based on new data on energy expenditure in infants, the World Health Organisation (WHO) reduced the recommended energy requirements for infants by 15 to 20 % [11]. Current formula-feeding instructions in UK are based on the previous 1985 WHO recommendations and this may be an important reason why formula-fed babies are at a greater risk of rapid weight gain and subsequent obesity than breastfed infants. Three meta-analyses of observational studies reported that obesity risk at school age was reduced by 15–20 % in breastfed compared with formulafed infants [12–14]. In 2006, the WHO published growth charts based on the growth of breastfed babies and recommends this lower plane of growth as the optimum standard for growth of all infants [15, 16]. While the benefits of breastfeeding are well recognised, the 2010 UK Infant Feeding Survey showed that only 21 % of babies were exclusively breastfed at age 6 weeks and 1 % at 6 months [17]. Hence in addition to supporting breastfeeding, it is important to optimise the growth of formula-fed babies.
Page 2 of 10
In the Baby Milk trial we aim to evaluate the efficacy, cost-effectiveness and acceptability of a theory-based, multi-component intervention to reduce formula-milk intake (based on the 2004 WHO recommendations for energy requirements) and prevent excess weight gain during infancy. We also aim to understand the psychological mediators of any effect of the intervention on formula-milk and energy intake.
Methods/Design Study design
The Baby Milk trial is an explanatory, parallel, individually randomised controlled trial of parents (mainly mothers) and their babies who are formula-fed. The focus of the primary outcome measurement is the baby, but the focus of the intervention is the caregiver. The intervention will commence when the baby is enrolled in the study (between 2 and 14 weeks) and be delivered up to 6 months. Babies will be followed up to age 1 year. In this explanatory trial, the intervention programme will be delivered by trained and quality-assured facilitators (research nurses). Participants in the control group will be offered the same number of contacts and standard advice about formula feeding, and weaning will be discussed. Ethical approval has been obtained from the Cambridgeshire 4 Research Ethics Committee (Ref:10/ H0305/9), and fully informed written consent will be taken from all participants. Recruitment and retention
Parents and their babies who are partially or fully formulafeeding within 14 weeks of birth will be identified by research staff on a postnatal hospital ward; health professionals, including GPs, midwives and health visitors; and via a mail-out using the National Health Service (NHS) database (SystmOne). Most babies in England are delivered in the hospital and looked after by a community midwife for the first 2 weeks after discharge from hospital. Subsequently, they come under the care of a health visitor who records if they are formula-feeding in the NHS database. This database will be used to send a participant information sheet to parents in the catchment area. Research staff and midwives will identify babies within 2 weeks of birth. General Practices (GP, nurse, and other practice staff) will invite participants at the baby’s 6-week health check and immunisation clinics. Parents who return a reply slip expressing an interest in taking part or finding out more about the study will be contacted by research staff at the Medical Research Council (MRC) Epidemiology Unit to answer any questions, check eligibility criteria, and where appropriate, invite them for their baseline visit (at 2 to 14 weeks age). GPs and health visitors will be informed by letter if a baby under their care has been recruited into the study.
Lakshman et al. Trials (2015) 16:442
Page 3 of 10
special formulas (soya-based, lactose-free, hydrolysed or anti-reflux formulas) at the time of recruitment will also be excluded; however, they will not be excluded if they are put on a special formula after randomisation.
Maximising retention is an important issue and regular (4 to 6 weekly) contacts with participants in both groups should reduce attrition. The information sheet will emphasise the importance of follow-up irrespective of group allocation and adherence to the intervention. Participants who drop out from the intervention will be encouraged to attend for outcome measurements. For participants who withdraw from the trial, any data collected up to the withdrawal date will be retained and safely stored, but contact details will be removed.
Measurements
A summary of the measurements undertaken is presented in Table 1. Anthropometry
Anthropometry data will be collected by trained research assistants using standard operating procedures. In order to minimise bias, the measurement team will be blind to group allocation and will be trained to avoid discussing this with parents. Parents will also be advised not to discuss allocation with the measurement team. Weight will be measured with the baby undressed, using Seca Infant Electronic Scales™ and recorded to the
Inclusion and exclusion criteria
All healthy, term infants who are receiving formula-milk within 14 weeks of birth will be eligible to participate. We will exclude low birth weight (
