Obesity is one of the greatest threats to health in the 21st century in many countries, including New Zealand. New Zealand is one of the five worst OECD countries for both child and adult overweight status , with almost 10% of children aged 5-14 years currently considered obese and a further 20% identified as overweight . Many parents do not recognise that their children are overweight [3, 4], and even if they do, long-term outcomes from interventions once children or adults are overweight are not impressive [5, 6]. In response to convincing evidence that early growth sets the pattern for future growth and predicts both childhood and adult obesity, as well as later cardiovascular morbidity and mortality [7–9], there has been an increasing focus on preventive interventions during infancy.
In designing interventions for the primary prevention of excessive weight gain in infancy, it appears logical to begin with the most obvious determinants of energy balance--energy intake (breastfeeding, complementary feeding, and infant diet) and energy expenditure (activity and sedentary behaviours). However, over the last 10 years, increasing evidence has also linked sleep problems, and in particular short sleep duration, with increased risk of excessive weight gain . An intervention that seeks to alter infant food, activity and sleep needs to effectively modify parental practices in these areas in order to positively influence infant behaviour. The following sections outline the justification for our approach.
Breastfeeding and introduction of complementary foods
Despite continued controversy, a recent review of systematic reviews of observational studies supports an association between no, or short, duration of breastfeeding and an increased risk of overweight and obesity to 5 years of age . Although the effect appears to be small--each additional month of breastfeeding may be associated with a 4% decrease in the odds of overweight --it does not appear to be explained by publication bias or confounding . Breastfeeding may be particularly protective against obesity if the breastfeeding is exclusive , or the mother is overweight . However, limited intervention studies have been performed and it is not possible to conduct a trial in which infants are randomised to receive or not receive breast milk. The PROBIT study was able to randomise maternity hospitals in Belarus to either a breastfeeding promotion based on the WHO-UNICEF Baby-Friendly Hospital Initiative, or standard practices and policies in place at the time of the study. Although the intervention group increased their duration of exclusive breastfeeding this had no effect on body mass index (BMI) at 6.5 years of age . However, caution must be exercised when applying these results to countries such as New Zealand, where obesity rates, and therefore the potential for prevention, are considerably higher.
It has been suggested that later introduction of complementary foods may be associated with lower percentage body fat at age 7 years  and decreased risk of adult overweight . However, this is controversial , with a number of studies finding no immediate effect on growth during infancy including two small randomised trials to 6 and 12 months of age [20, 21]. More recently, a longitudinal study following Australian infants from before birth to 10 years of age found that delaying the introduction of solids from 20 to 24 weeks of age was associated with a 10% lower odds of overweight or obesity at 10 years from multivariate modelling . The authors propose potential mechanisms, including epigenetic modification of metabolic programming and effects of excess protein intake on age of adiposity rebound that may account for a delayed effect on obesity, even in the absence of an immediate effect on body weight.
Food and eating
Early studies clearly demonstrated that children are born with an ability to self-regulate intake to match physiological needs . However, the rising prevalence of overweight in toddlers and preschool-aged children and the current mismatch between energy intake and requirements  would suggest that this ability is either lost or ignored from fairly early in life. The potential role that parents play in encouraging appropriate eating is thus of considerable interest. In feeding terms, responsive parenting refers to a parent promoting a pleasant feeding environment and responding to hunger and satiety cues in their offspring. By contrast, unresponsive parenting involves over-control from the parent such as pressuring the child to eat or overtly restricting foods, too little control of the child's eating (uninvolved feeding), or too much control by the child (indulgent feeding) . The majority of studies investigating responsive parenting in young children demonstrate significant inverse relationships with body weight . Ideally parents play a role in helping children develop appropriate food preferences by offering a range of healthy foods, on a number of occasions, and in a relaxed environment .
Factors other than parenting style have also been implicated in excessive weight gain during the early years, including family meals, portion size, and consumption of sweetened beverages. Family meals are associated with healthy eating patterns  and reduced obesity  in children and adolescents. However, the relative effects may differ across ethnic and socioeconomic groups  and any positive effects of shared mealtimes may be mitigated by having television on at the same time . Although the precise mechanisms remain to be elucidated, eating together allows modelling of eating practices, is predictive of family connectedness and presumably facilitates communication.
Portion size has also been implicated in the development of obesity  and experimental studies consistently demonstrate that offering larger portions of energy-dense foods results in a greater intake of food, at least in the short-term [32, 33]. In contrast, providing larger portions of low energy-dense foods (fruit and vegetables) increases the overall intake of these foods, without increasing total energy intake for the meal . However, educating parents about appropriate portion sizes for children is complicated by a lack of awareness or indeed concern about age-appropriate portion sizes for children . Furthermore, although earlier work suggested that preschool-aged children may be relatively immune to the obesogenic effect of increased portion size , more recent studies highlight that energy dysregulation may occur as early as 12 months of age [37, 38]. Training parents to recognise and respond to hunger and satiety cues in their infants in an effort to encourage appropriate food consumption independently of portion size is therefore of considerable interest.
The relative contribution of sweetened beverages to the development of obesity is controversial [39, 40]. There is no doubt that intakes of sweetened beverages have increased substantially over time in all age groups, at least in the US where the majority of infants aged 6-24 months consume sweetened beverages, predominantly fruit juice or fruit drinks (6 ounces/day) with smaller intakes (1.5 ounces/day) of other sweet drinks , at a time when obesity rates have risen. Certainly there appear to be links between consumption of sweet beverages and body weight in older preschool children .
Physical activity and sedentary behaviours
Engaging in more sedentary activities (including television viewing) and less outside play have also been linked to the development of obesity with some evidence suggesting that less active pre-school children remain less active than their peers throughout childhood . Although it is commonly believed that young children are very active, studies utilising objective measures of physical activity (accelerometry) demonstrate that even preschool aged children spend a large portion of their day in sedentary activities, as do older children and adolescents [44, 45]. Expert groups currently recommend exposing infants to prone play or "tummy time" to help facilitate motor milestone development, and limiting the time spent restrained in car seats, strollers, prams, and play pens . However many parents do not encourage prone play in their infants, because of either infant resistance, or misperceptions around positioning during sleep (prone not recommended) and awake (prone recommended) .
Despite recommendations from expert groups to discourage television viewing in children under two years of age , television viewing is common in this age group . This applies to even the youngest infants, with 40% of 3 month olds viewing television, a proportion that increases with age so that 90% of 24 month old children are watching television regularly . Exposure to television in the infant and toddler years has been associated with irregular sleep patterns  and poorer dietary habits , and may impair later language and cognitive development , and predispose children to obesity . Interventions to reduce television viewing in the first few years of life show promising effects on the time spent watching television [55, 56].
At birth, the sleep of term infants is considered polycyclic, i.e. there are multiple sleep periods and wake periods in a 24-hour day. On average, infants from birth to 2 months sleep approximately 15 h with short periods of waking . Gradually infants consolidate their sleep into nocturnal sleep and daytime wake, coincident with maturation of sleep-wake regulatory systems within the brain circuitry. However, behavioural or physiological factors can intervene to upset sleep-wake regulatory systems, resulting in problematic sleep. Parenting is proposed to play a key role in sleep-wake regulatory systems . Sleep problems within the normal (non-clinical) population fall into the categories of: 1) insomnia (difficulty getting to sleep); 2) poor sleep maintenance (difficulty staying asleep), and; 3) sleep fragmentation (frequent night waking). Sleep problems can result in a shorter than normal sleep duration measured over a 24-hour period (termed "short sleep duration").
Adequate sleep in infancy and childhood is important for physical and psychosocial growth and development. A number of cross-sectional and longitudinal studies have linked short sleep duration with the development of obesity [10, 59, 60]. Moreover, as obesity rates have increased over the last one or two decades, some longitudinal studies have reported a significant decline in sleep duration [61, 62] possibly associated with modern lifestyle.
Sleep difficulties in early infancy are common (25-35% prevalence) and can be transient but those unable to achieve a sleep duration of 6 h by 5 months of age have a much greater risk of short sleep duration and sleep problems later in childhood [63, 64]. Moreover, sleep problems often co-exist with feeding difficulties . There are proven strategies for preventing and treating sleep problems in infancy , which may also decrease postnatal depression in mothers and improve family well-being . However, their potential impact on growth and obesity is not known. In one study these sleep interventions did not appear to affect growth  but the effects of the sleep intervention on parent-reported sleep problems were not large, there were no objective measures of sleep, and growth outcomes were not part of a pre-planned analysis. Paul et al. , however, report a pilot study of a combination infant sleep intervention and weaning intervention that had a significant effect on weight for height centiles at 1 year of age with the mean weight for height centile in the combined intervention group being the 33rd centile compared to the 50th centile for the comparison group.
At least 9 genes have been associated with obesity in childhood , and at least one of these seems to influence appetite . As genes and environment interact at many levels, it is important to assess the more common genetic loci increasing the risk for excessive weight gain in large intervention studies.
All parenting practices, including those around infant food, activity and sleep, are influenced by parenting style, a psychological construct representing standard strategies that parents use in their child rearing. Parenting style is characteristic of the parent, is not altered by the child, is stable over time and acts as the context that moderates the influences of specific parenting practices . It is therefore important to investigate the relationship between parenting style and the success of any behaviour intervention. Managing children's behaviour is a fundamental part of parenting, and disciplinary practices within families that can have a lifelong effect on children's well-being . Surprisingly few studies have explored the emergence of discipline practices in the first few years of life and those authors who have, have focused on physical discipline [74, 75]. More recently, research has suggested that punishment of any type, and verbal aggression, may have the same adverse effects on well-being as physical discipline . Several American studies have claimed that as many as a third of parents reported yelling at infants before they were nine months of age and twice this number between 19 and 35 months [77, 78]. As education and support around the areas of feeding, activity and sleep are part of broader parental efforts to modify child behaviour, examining the potential effects (either positive or negative) on child discipline of any intervention that affects parenting behaviour is warranted.
The aim of this study is to evaluate the effect on weight velocity and body mass index at 24 months of age of two early childhood obesity prevention interventions delivered to parents in late pregnancy and the first 2 years of their infant's life: anticipatory guidance, extra education and support to encourage (a) positive diet and physical activity behaviours, or (b) appropriate sleeping patterns, or (c) both interventions combined.