Overweight and obesity are responsible for a large proportion of morbidity and mortality among the adult population [1–3]. While overweight and obesity typically become more common and severe, and have their greatest impact, later in life, longitudinal studies have shown that they have even more significant adverse effects when acquired early in life [4, 5]. The age of onset and severity of overweight and obesity in childhood is related to its persistence into adulthood, with obese children having at least a 25–50% risk of progressing to obesity in adulthood .
There is overwhelming evidence of increasing high prevalence of childhood overweight and obesity over the past two or three decades, in particular, among children aged 2 to 5 years internationally [7–9]. In Australia, a recently published study, from Wave 1 of the Longitudinal Study of Australian Children , involving 4983 children aged 4–5 years, showed that 15.2% were overweight and an additional 5.5% were obese, with children from lower socioeconomic backgrounds having higher prevalence rates. In addition, a study of young children aged 2–4 years in Melbourne and Sydney found that about one in six were overweight or obese .
The rising prevalence of childhood obesity, its appearance in early life and the modest impact of interventions aimed at children with existing overweight [12, 13], underline the imperative for an effective, home-based approach to prevent overweight and obesity in early childhood. However, few systemic interventions aimed at preventing early childhood overweight and obesity have been implemented and evaluated [12, 14]. Although existing infant nutrition programs address overweight and obesity to some extent [15, 16], this has not been the main focus of such interventions to date and nor has this particular aspect been evaluated. In addition, there has been little research or practice in the area of physical activity promotion in infancy and early childhood . As with adults, an explicit aim of increasing physical activity and decreasing sedentary behaviour is likely to be required if obesity prevention is to be addressed.
The contributing factors
While underlying genetic factors may predispose to overweight and obesity, the overarching cause is chronic energy imbalance – excessive energy intake and inadequate energy expenditure . Behavioural factors such as artificial feeding (bottle feeding), dietary fat intake, sweetened drink intake, family eating patterns, levels of physical inactivity and television viewing have been identified as major contributing factors for childhood obesity . There is also some evidence that overweight and obesity are more prevalent in lower socio-economic groups [10, 19]. This may be due to poorer dietary and physical activity behaviours that are associated with social disadvantage, or it may be associated with some other aspect of social disadvantage that is less well understood.
The evidence also suggests that sustained breastfeeding, the appropriate introduction of solids, the avoidance of the use of less healthy foods and sweetened drinks as a reward, a comfort or a "pacifier", a reduction in sedentary behaviour and the encouragement of physical activity can contribute to the prevention of overweight in early childhood [20, 21].
However, focusing on diet and physical activity alone may not be sufficient to explain the development of overweight in early childhood. The context of the parent-child feeding interaction and the environmental context for energy expenditure need to be considered for obesity prevention to be maximally effective. Energy imbalance results from complex interactions and in children the role of parents is, of course, paramount.
Infant feeding and awareness of childhood obesity
To deepen our understanding of mothers' attitudes, beliefs and experiences about the issues related to infant feeding, we conducted a study as part of the needs assessment for developing this program . The study showed that while there was good overall awareness of the recommendations about the duration of breastfeeding and the introduction of solids, many mothers were not acting on these because of various misconceptions about milk supply, the effect of solids on sleep, interpretation of the baby's behaviour as an indicator of his or her readiness for solids, and a general lack of understanding of the possible consequences of not following infant feeding guidelines. The overwhelming amount of confusing and often conflicting information from a variety of professional and social sources led women to the conclusion to "do what works for us". Using food for rewards was a common experience for most mothers, and although there was agreement about the potential dangers and inappropriateness of this practice, this was outweighed by the convenience and practicality. Finally, the study concluded that most mothers did not even consider that the early onset of childhood obesity was an issue . Other studies have shown that even parents of overweight children fail to recognize excess weight as a health issue for their children .
Home visiting programs
Home visiting programs, which provide social support to first time mothers, have been established as effective interventions for improving the health and wellbeing of parents and children [24–27]. These programs have been widely promoted as a means of preventing a range of health and developmental problems in children from vulnerable and disadvantaged families. Research evaluating early intervention strategies highlights the need for programs such as home visiting to be a part of broader strategies for promoting healthy family functioning and social support . Family functioning has been found to be determined by a range of factors including the quality of relationships, the health of family members and the presence of life stressors. Social support is determined by the availability of others to share problems and feeling close. Home visits provide the opportunity for parents to address family functioning problems with others as well as providing social support. To have lasting beneficial effects, Ramey and Campbell suggested that the intervention needs to start early, preferably before the child is born, and to continue beyond the first two years of the child's life, providing continuing support until the child starts school .
Home visiting has been adopted as one of the strategies in the NSW Families First initiative. Families First is the NSW Government's prevention and early intervention program to help parents give their children "a good start in life" . Its main concerns are to improve the general health of mothers and babies and to build communities that work to support families. In NSW all new mothers are offered one home visit from Early Childhood Services within a month of the birth of a child. It is intended for vulnerable families to receive multiple home visits for at least two years.
The home-based early intervention to prevent childhood obesity
In this proposed study we will implement and evaluate a structured intervention specifically addressing the issues of childhood obesity to be delivered by an early childhood health nurse during the first two years of life. The intervention has been developed and refined through a series of parallel processes. First, a pilot program has been completed with some promising results . The program was very well received by the participating mothers, with a retention rate of 95% over a year. Compared to the state population average, the rate of breastfeeding at 12 months was significantly higher (36% vs 18%, χ2
1 = 8.21, P < 0.01), there was a lower rate of the introduction of solids before 4 months (2% vs 13%, χ2
1 = 8.73, P < 0.01), and there was a high rate of cup feeding at 12 months (98%).
Second, existing evidence of the effectiveness of interventions has also informed the development of this program, such as the lessons learned by various studies in working with families of overweight children, and the dynamics of child feeding [12, 13, 15, 16]. In addition, health promotion theories, such as the Health Belief Model, have been applied in informing the development of the intervention to increase perceptions of susceptibility of children being overweight and social learning models including attention to social support and relapse prevention. The series of topic specific interventions has been planned using an eclectic theoretical approach based on all that is currently known about the dynamics of child feeding, other behaviours and their effect on weight.