Relationship between maternal obesity and infant feeding-interactions
Abstract
Background
There are no data regarding the relationship between maternal adiposity and interaction and feeding of infants and possible contribution to childhood obesity. In this study we determined the relationship between maternal body weight and composition and infant feeding patterns and maternal-infant interaction during 24-hour metabolic rate measurements in the Enhanced Metabolic Testing Activity Chamber (EMTAC).
Methods
The amount of time four obese (BMI = 33.5 ± 5.3 kg/m2) and three normal weight (BMI = 23.1 ± 0.6 kg/m2) biological mothers, spent feeding and interacting with their infants, along with what they ingested, was recorded during 24-hour metabolic rate measurements in the EMTAC. The seven infants were 4.9 ± 0.7 months, 69 ± 3 cm, 7.5 ± 0.8 kg, 26 ± 3 % fat and 29 ± 25 percentile for weight for length. Energy and macronutrient intake (kcal/kg) were assessed. Maternal body composition was determined by air displacement plethysmorgraphy and that of the infants by skin-fold thicknesses. Pearson correlations and independent t-tests were utilized for statistical analysis (p <>
Results
Infants born to obese biological mothers consumed more energy (87.6 ± 18.9 vs. 68.1 ± 17.3) and energy as carbohydrate (25 ± 6 vs.16 ± 3; p < r =" 0.73;p" r =" -0.98;" r =" -0.92;">
Conclusion
Greater maternal body weight and percent body fat were associated with greater infant energy intakes. These infants were fed less frequently and consumed more carbohydrates in a shorter period of time as compared to infants from normal weight biological mothers. These variations in feeding patterns may predispose certain infants to obesity.
Introduction
Childhood obesity is now recognized as a national health epidemic, doubling among children 6–11 years old between the last (1976–1980) and the present (1999–2000) National Health and Nutrition Examination Surveys. Obesity in early childhood leads to more severe adult obesity [1]. Overweight and obese children are facing adult onset disease type risk factors such as cardiovascular heart disease, elevated blood pressure and type II diabetes [2]. Presently, type II diabetes represents 8–45% of all new cases of diabetes diagnosed in children and adolescents [2]. This epidemic increase in childhood obesity can only lead to a lower quality and duration of life and increased health care costs [3,4].
Many studies have identified the influence of genetics and environmental factors on potential causes of childhood obesity [5,6] and [7]. Some of these include having obese biological parents [8] and biological mothers being of a low social economic status [9,10]. There are other factors in early infancy that may also contribute to obesity in childhood. For example, being born small or large for gestational age [11], breast feeding less than three months [12], exposed to early introduction of complementary foods [13] and/or excess fruit juice consumption [14]. There may be many other potential factors that may contribute to childhood obesity but as yet undiscovered.
The relationship between maternal body composition and infant and maternal interaction and feedings have not been studied. Obese biological mothers may interact in such a way as to possibly contribute to greater energy intake in their infants earlier in life. Recently we published the results of 24-hour metabolic measurements in four-to-six month old infants in the Enhanced Metabolic Testing Activity Chamber (EMTAC) [15]. This study allowed collection of data to assess the relationship between maternal body composition and infant feeding and interaction patterns.
Methods
Subjects
The data for this analysis were derived from a previous study of 24-hour metabolic rate and physical activity in infants. Data from seven infants were complete in regards to metabolic rate, physical activity and body composition in both the infants and biological mothers. Moreover, complete data in regards to complementary food or formula intake were available. The physical characteristics of the biological mothers are shown in Table 1 and that of their infants in Table 2. Biological mothers were classified as obese (BMI >30 kg/m2) or of normal weight (BMI <>2) [16]. The mothers and their infants were recruited from the Outpatient Clinic of Miami Children's Hospital in
Table 1. Physical characteristics of normal and obese biological mothers
Table 2. Physical characteristics of infants born to normal weight and obese biological mothers
Maternal Anthropometry
Maternal height was measured using an Ayrton Model S100 hospital grade stadiometer (QuickMedical Inc.,
Infant Anthropometry
On the day of the study supine length (crown to heel) was measured in duplicate with a horizontal stadiometer (Perspective Enterprises, Kalamazoo, MI) and body weight was the average of two measurements obtained with an infant scale (Cardinal Detecto, Webb City, MO). Skin-fold thicknesses were the mean of two measures at each of five sites (biceps, triceps, sub scapular, flank and quadriceps) on the right side of the body using a Lange skin-fold caliper (Beta Technology, Cambridge, MD) according to a standard procedure [18]. Body fat and fat-free mass were calculated by appropriate equations [19].
Maternal interaction and infant feeding patterns
Energy and macronutrient intakes were determined from the formula and infant food manufacturer's proximate analysis for the nutrient components [20]. The amount of each food consumed by the infant during the 24-hour period was recorded. The actual amount of formula consumed by the infant was determined using calibrated infant feeding bottles and the amount of complementary feeding was also determined. The recording of energy and macronutrient intake started one-hour prior to and ended one-hour before the conclusion of the 24-hour metabolic testing period. The one-hour off-set was necessary to include or exclude energy consumed before and after the metabolic testing period which compensates for variations in feedings and the intestinal transient time in this age group of infants [15].
Only the biological mothers were present and cared for, fed and interacted with infants during the entire 24-hour testing period. During metabolic testing, biological mothers continued to feed their infants at their discretion in the same manner as before the study. They brought the milk formula and complementary foods they selected to the laboratory. The biological mothers were advised not to alter their infant feeding practices for the duration of the study. All infants born to normal weight biological mothers and one from an obese biological mother were only formula fed prior to and during metabolic measurements. Three out of the four infants born to obese biological mothers were receiving complementary foods beginning just after four months of age and were fed such during the study. The complementary foods included rice cereal, mixed vegetables, Beachnut® apple sauce and dessert fruit pudding. Six of the infants were fed Carnation Good Start® with iron while one was fed Carnation Alsoy®.
One member of the research team in charge of the 24-hour metabolic study was always directly involved with the testing procedure and was in close proximity to the infant and available to parents to address questions and concerns during the 24-hour period. The investigators acted as observers and recorded infant feedings, amount and type of formula fed along with consumption of complementary foods. Upon completion of the 24-hour metabolic measurement, macronutrient intake was determined from the amount of formula or complementary food fed utilizing the manufacturer's proximate analysis. This methodology of determining nutrient intake is valid and has been utilized in several previous studies in infants [21,22] and adults [20,23]. Investigators also recorded the interaction time and type of interaction and the observed periods of infant sleep. Furthermore, any other contact with the infant during the entire 24-hour testing period was also recorded.
The mean amount of time infants spent feeding was calculated by taking the sum of the time of all feeding periods and dividing by the number of feedings over the 24-hour testing period. The mean time between feedings during the day was calculated by taking the sum of the time intervals between each feeding session from 9:30 AM -11:30 PM and dividing by the number of feedings over the same period. The day and night periods were chosen to conform to the standards of previous 24-hour metabolic studies [24,25]. The mean time between feedings for the entire testing period was calculated in a similar manner but included all feedings over the course of the 24-hour metabolic measurement.
Interaction time was calculated by taking the sum of all data summary periods were the biological mother was interacting with her infant. Each data summary period was a five minute mean of continuous measurements of energy expenditure and physical activity index. The 24-hour testing period consisted of 288 five minute data summary periods. Interaction recorded included feeding, holding and cuddling the infant as well as diaper changes. In a similar manner the total amount of interaction time by biological mothers one hour prior to feeding was calculated by taking the sum of all summary periods one hour prior to each feeding episode. Finally, the total time infants spent engaged in feeding was calculated by taking the sum of all summary periods were the infant was being fed [15]. Feeding included all formula and complementary foods.
Measurements of metabolic rate and physical activity
Biological mothers were given instruction on how to interact with their infants while in the EMTAC and was allowed time to practice using the hand access ports prior to metabolic testing (Figure 1). Once all of the instruction and instrument calibrations were completed each infant was placed in the EMTAC for 24-hours from 9:30 AM till 9:29 AM the following day for continuous measurements of energy expenditure (EE; kcal/min) and physical activity (PA; oscillations in weight/min/kg body weight) as described previously [15]. Any supplies such as diapers, formula, complementary infant foods or toys were placed in the EMTAC in hanging bags before the start of the test. The mother of the infant being studied was provided lodging within the laboratory during the entire testing period. There were no restrictions in regards to room lighting, feeding or interaction of the infant or with any of the activities of the family during the entire testing procedure.
Figure 1. Photos showing the interaction between the biological mother and her infant utilizing the hand access ports of the EMTAC.
Energy expenditure (kcal/min) was continuously calculated during metabolic testing according to the method of Jequier [25] and summarized every five minutes as described previously [26]. At the conclusion of each metabolic test, all metabolic data were corrected for parental interaction, prior to the calculation of resting (RMR; kcal/kg/day) and sleeping metabolic rates (SMR; kcal/kg/d) as described previously [15]. All metabolic results were expressed as kcal/kg body weight/day.
The small number of infants in the study was due to the difficulties in recruiting biological mothers willing to stay in or around the laboratory for almost 30 hours. This time was necessary to instruct the biological mothers on how to interact and feed their infants using the hand access ports of the EMTAC and allow practice sessions prior to the start of the 24-hour metabolic measurement. Furthermore, body size and composition measurements had to be obtained for both the infants and biological mothers prior to the metabolic test. Moreover, the EMTAC had to be prepared and calibrated prior to the start of the 24-hour metabolic measurement.
Statistical Analysis
Person correlations were used to determine the relationship between the mother's anthropometry and interaction time and energy intake. Independent t-tests were used to determine differences in all metabolic and feeding parameters studied between obese and non-obese biological mothers. Significance (p <>
Results
Height and age were similar among the normal weight and obese biological mothers. The latter had a greater body weight, BMI and percent body fat (Table 1) in comparison to their normal weight counterparts (p < name="IDANHHZD">2). The similarity of the infants in terms of growth performance at the time of the study was further verified by the lack of significant differences in Z-scores obtained for weight for length, weight for age and length for age percentiles. None of the growth assessment parameters of the infants were more than 0.4 standard deviations from the mean.
Infants born to obese biological mothers consumed more energy, and energy as carbohydrate, than their normal weight counterparts (Table 3). Three, out of the four infants born to obese biological mothers consumed complementary foods. The amount of energy consumed from complementary foods by these infants of obese biological mothers was 18.3 ± 2.5 kcal/kg. This was in addition to the energy intake of 69.1 ± 20.3 kcal/kg from formula for these same infants. However, energy intake from protein and fat, for both complementary feedings and formula, were similar among the two groups (Table 3). The amount of formula intake was also similar (90.1 ± 16.3 vs. 98.9 ± 35.4 ml/kg) between the infants born to obese and the normal weight biological mothers. There was a significant (p < r =" -0.73;" name="IDA1HHZD">2a).
Table 3. Nutrient intake and feeding profile for the infants born to normal weight and obese biological mothers
Figure 2. Correlation between 24-hour energy intake (kcal/kg/d) with both maternal body weight (kg; Figure 1a top plot) and body fat (%; Figure 2b bottom plot) for the seven infants in this study.
Obese biological mothers spent less time interacting and feeding their infants over the course of the 24-hour testing period (Table 3). There was a negative correlation between total 24-hour interaction time and both maternal body weight (r = 0.98; p < name="IDAVPHZD">3a) and body fat (r = 0.92; p < name="IDAZPHZD">3b). Moreover, overweight biological mothers spent less time interacting with their infants one hour prior to feeding (Table 3). The pattern of maternal interaction over the course of the 24-h testing period is shown in Figure 4. Normal weight biological mothers interacted with their infants more over the course of the 24-hour testing period than the obese biological mothers (Figure 4). When considering just the hour prior to each feeding, normal weight biological mothers interacted with their infants more than their obese counterparts (Table 3). The increased interaction was more significant (p < name="IDAQYHZD">4). Finally, infants of overweight biological mothers spent more time sleeping (Table 3) than their normal weight counterparts.
Figure 3. Correlation between interaction time (minutes) with both maternal body weight (kg; Figure 1a top plot) and body fat (%; Figure 1b bottom plot) for the seven infants in this study.
Figure 4. Twenty-four hour interaction profile for infants born to normal (top) and obese (bottom) biological mothers. The Y-axis represents the mean amount of interaction time over each five minute period. There are 288 five minute summary periods during a 24-hour metabolic measurement. A Obese biological mothers spent less time (p <>
The number of feedings and the amount of time necessary for each meal tended to be less for the infants of obese biological mothers, however, these differences were not significant (Table 3). There was also a tendency for infants of obese biological mothers to consume more energy at each feeding in comparison to those of normal weight mothers. Furthermore, infants of obese biological mothers tended to allow more time in between feedings during the day and over the entire 24-hour testing period (Table 3).
There were no significant differences in any of the metabolic parameters between infants from obese and normal weight biological mothers (Table 4). However, there was a tendency for a higher respiratory quotient and a greater amount of physical activity in those infants born to obese biological mothers.
Table 4. Twenty-four hour metabolic rate and physical activity of infants born to normal weight and obese biological mothers
Discussion
In this study we demonstrated through direct observation that infants born to obese biological mothers ingested more energy and a greater amount of that energy were derived from the carbohydrates present in complementary foods. Furthermore, increased maternal body weight and fatness were related to increased 24-hour energy intake. Moreover, increased body weight and fatness of the biological mothers resulted in a decline in the amount of time spent interacting with their infants during the 24-hour testing period. This included less time spent feeding the infant, and particularly a lower amount of interaction one hour prior to feedings.
The biological mothers were able to freely interact with their infants in a comfortable setting. However, none of the biological mothers reported being uncomfortable with their infant being in the EMTAC or staying at the laboratory during the metabolic testing. Furthermore, they did not report any difficulties in interacting or feeding their infant utilizing the hand access ports of the EMTAC. Nonetheless, it is possible that the unfamiliar surroundings of the metabolic laboratory might have contributed to some changes in infant feeding practices not present in their maternal home setups.
Excess energy consumption early in an infant's life of those born to obese mothers, possibly accelerated with complementary food intake, might set the stage for future childhood obesity. In this study, there were no significant differences in infant body weight or composition between four to six months of age among the two groups of infants studied. However, infants of obese biological mothers consumed an average of 19.7 kcal/kg body weight more than the infants born to normal weight mothers during this study. Assuming that approximately 4900 kilocalories are needed per kilogram of body weight gain [27], it would take the infants of obese biological mothers a considerable amount of time to become obese if they would continue ingesting this amount of excess calories each day. This might explain why investigators report that it takes up to two years before a noticeable gain of body fat is observed in young children [1,28]. In overfed adults 66% of body weight gain is fat while the remainder is fat-free mass [29]. It is possible that overfeeding infants over a long period of time causes excess body weight gain of similar composition. However, no studies to date have quantified the composition of body weight gain in overfed infants from the time of birth.
Early introduction of complementary foods might increase body weight gain. In one study, early introduction of complementary foods was associated with greater infant body weight gain [30]. Other investigators [31] reported that complementary foods introduced to infants between 9 and 16 weeks showed a slight increase in weight gain velocity (g/week) in comparison to those infants who were introduced to these foods after 25 weeks. Both of these studies [30,31] suggest that early introduction of complementary foods might increase body weight gain. Therefore, early introduction of complementary foods, coupled with the increased energy intake at each feeding in the infants from obese biological mothers, as seen in our study, might set the stage for future childhood obesity. However, we did not have data to ascertain why obese mothers started complementary feedings in their infants.
Infants may be introduced to complementary foods at different times. In the Feeding Infants and Toddlers Study (FITS), 71% of the parents reported introducing complementary foods to their infants between four and six months of age while the other 29% reported introducing these foods to their infants at less than four months [32]. In another study were the National Health and Nutrition Examination Survey (NHANES III) data were analyzed, less than 25% of the parents reported feeding complementary foods to their infants prior to four months of age [33]. Moreover, the parents in both of these studies [32,33] were similar in regards to social economic status, age and ethnic background. In our study we did not have data on why obese biological mothers were feeding complementary foods to their infants. Moreover, neither the FITS [32] nor the NHANES III [33] studies related infant feeding practices to maternal body composition.
There were no significant differences in any of the metabolic parameters measured such as 24-hour energy expenditure, resting and sleeping metabolic rates, respiratory quotient and the index of physical activity. Moreover, there were no differences in any of the growth parameters (weight for length, weight for age and length for age percentiles) between the two groups of infants at the time of the study. Our results are in agreement with Stunkard et al [28] who found no differences in growth parameters, body composition, total energy expenditure by doubly labeled water, sleeping metabolic rate or physical activity in infants born to obese (greater than the 66th percentile for BMI) or lean (<33rd percentile for BMI) biological parents throughout the first year of life. In contrast to our results and those of Stunkard [28], Roberts et al [8] found reduced total daily energy expenditure in infants born to obese parents as determined by the doubly-labeled water method. The reduction of total daily energy expenditure was due to less physical activity in these infants [8]. It is possible that less interaction between obese mothers and their infants [8] accounted for the reduction in physical activity.
Since infants gain approximately 5 g/kg of body weight per day at four months of age [34], it is possible that constant additional caloric intake of those infants born to obese biological mothers will be manifested as additional daily body weight gain later in life. All these data suggest that maternal influences on infant body composition may not appear initially as obvious physical differences during the first six months of life. It is possible that the differences detected among biological obese mothers and their infants could affect the body composition of their infant as they age.
There may be other factors beginning in infancy that may be associated with the eventual increase in adiposity in later life. For example, fewer, but larger feeds and a higher sucking pressure were associated with greater adiposity in toddlers at two years of age [13]. This is in partial agreement with our results were we found that obese biological mothers spent less time interacting and feeding their infants. Moreover, infants from obese biological mothers consumed more energy in less time at each feeding. It is possible that the infants were hungrier due to the longer time between feedings.
Another study reported that greater maternal BMI during the first trimester of pregnancy was related to a higher prevalence of obesity in children from two to four years old. This is equivalent to 1 out of 4 children of obese mothers becoming obese as opposed to only 1 out of 10 children from normal weight mothers [35]. Moreover, it was also reported that a greater maternal BMI was a modest predictor of their daughter's relative weight at five years of age [36]. All of these studies [13,28,36] relate possible maternal influences upon future obesity of their infants. However, none eluted to the actual difference in the care of infants from either normal or obese mothers such as found in our analysis.
The association between the physical characteristics of biological mothers and their infants has not been ascertained. Six studies found no relationship between maternal BMI and infant's body weight after the first year of life [35,37-41] while two found such a relationship [42,43]. None of these studies accurately measured maternal body composition and did not include direct observation of the interaction dynamics between mothers and their infants. This was done in our study using air displacement plethysmography for maternal body composition and direct observation of food intake and feeding patterns including the number and length of infant feedings and the amount consumed at each meal during the entire 24-hour period. Additionally the type and length of maternal interaction with their infants revealed significant differences between normal weight and obese biological mothers which may not have been elucidated by other means. Though there were a small number of infants studied the results suggest that differences do exist on how mothers interact with their infants, depending on their body composition.
Conclusion
This study provided some new insight as to possible influences, beginning in infancy, as to the possible causes of childhood obesity. We have found additional factors that may contribute to future childhood obesity. The ability to conduct 24-hour metabolic rate measurements and direct accurate recordings of the biological mother's interaction with their infants elucidated specific differences in the care of infants that were related to maternal body weight and adiposity.
Abbreviations
EMTAC = Enhanced metabolic testing activity chamber
ANOVA = Analysis of Variance
BMI = Body mass index
EE = Energy expenditure
EI = Energy intake
RMR = Resting metabolic rate
SMR = Sleeping metabolic rate
PA = Physical activity index
RQ = Respiratory quotient
CHO = Carbohydrates
PRO = Protein
FITS = Feeding Infants and Toddlers Study
NHANES = Nutrition Health and Nutrition Examination Survey
Competing interests
The author(s) declare that they have no competing interests.
Authors' contributions
Dr. Russell Rising has contributed to the design of the experiment and conducted the data analysis. Furthermore, he either participated in some of the actual data acquisition or supervised pediatric research fellows in this regard. He also assisted in the preparation of the small grants necessary for funding of this project. Finally, he also assisted in the writing and editing of this manuscript.
Dr. Fima Lifshitz directed the research and contributed to the preparation of the manuscript and assisted with data analysis. He also generated some of the grant proposals necessary for the financial support of this study. Both authors were involved in the final writing of this manuscript.
Acknowledgements
This work was supported in part by NIH grant (#1R43HD/DK38180-01A2) and by Pediatric Sunshine Academics
abstract
Background
Multiple factors combine to support a compelling case for interventions that target the development of obesity-promoting behaviours (poor diet, low physical activity and high sedentary behaviour) from their inception. These factors include the rapidly increasing prevalence of fatness throughout childhood, the instigation of obesity-promoting behaviours in infancy, and the tracking of these behaviours from childhood through to adolescence and adulthood. The Infant Feeding Activity and Nutrition Trial (INFANT) aims to determine the effectiveness of an early childhood obesity prevention intervention delivered to first-time parents. The intervention, conducted with parents over the infant's first 18 months of life, will use existing social networks (first-time parent's groups) and an anticipatory guidance framework focusing on parenting skills which support the development of positive diet and physical activity behaviours, and reduced sedentary behaviours in infancy.
Methods/Design
This cluster-randomised controlled trial, with first-time parent groups as the unit of randomisation, will be conducted with a sample of 600 first-time parents and their newborn children who attend the first-time parents' group at Maternal and Child Health Centres. Using a two-stage sampling process, local government areas in Victoria, Australia will be randomly selected at the first stage. At the second stage, a proportional sample of first-time parent groups within selected local government areas will be randomly selected and invited to participate. Informed consent will be obtained and groups will then be randomly allocated to the intervention or control group.
Discussion
The early years hold promise as a time in which obesity prevention may be most effective. To our knowledge this will be the first randomised trial internationally to demonstrate whether an early health promotion program delivered to first-time parents in their existing social groups promotes healthy eating, physical activity and reduced sedentary behaviours. If proven to be effective, INFANT may protect children from the development of obesity and its associated social and economic costs.
Trial registration
Current Controlled Trials ISRCTN81847050
Background
Preventing the development of obesity in children is an international health priority [1]. Current estimates suggest that the prevalence of overweight and obesity in all age groups is rapidly increasing worldwide [2]. In Australia approximately 25% of children are overweight or obese and that estimate is growing with data highlighting that these increases begin in early childhood [3]. An Australian sample of 114,669 pre-schoolers showed the prevalence of overweight and obesity increased from 16.3 to 27.2 per cent in girls and from 13.4 to 21.4 per cent in boys between 1995 and 2002 [4].
Overweight and obesity are recognised to have numerous negative impacts on children's health and wellness during childhood and through to adult life [5,6]. Further, research has shown that adiposity within the childhood period is a stable trait [7] and that parents are often poor at identifying fatness in their children [8]. In addition, obese children tend to become obese adults and treatment is difficult and costly [2]. Cochrane reviews have established that opportunities for prevention are poorly understood [9]. Overall there is an urgent need for research on the capacity to influence the development of children's obesity- promoting behaviours in early life.
Overweight in early childhood is determined in part by eating, physical activity and sedentary behaviours learnt at home in the first five years of life. The intervention outlined is informed by the understanding that (a) obesity-promoting behaviours are established early in life, (b) parents play a primary role in shaping these behaviours in infancy, (c) intervening before these behaviours (and parents responses to them) are established is likely to be effective, and (d) that the social milieu provided by parent groups is likely to facilitate and support the uptake of health promotion messages.
Obesity-promoting behaviours are established early in life
Recent evidence highlights that obesity-promoting dietary habits, such as high consumption of energy-dense foods and fluids, previously documented in children [10,11] are also evident in infants and toddlers [12]. Australian data using 3-day weighed food records (n = 538), shows 90% of 18-month old children consumed energy-dense snack foods on the recall days and 70% consumed sweetened non-milk drinks (e.g. soft drinks) [13]. Overall, foods considered as "extra" or "non-core" provided 27% of the total energy intake in that sample. In addition, the nutritional quality of diet is known to continue to decline throughout childhood and adolescence [14,15].
These early dietary patterns couple with evidence of high levels of sedentary behaviours in early childhood. For example, 17% of 0–11 month and 48% of 12–23 month old children in the US watch more than the recommended two hours of television per day, and this proportion increases throughout childhood [16]. Further evidence suggests that viewing television for more than two hours per day is positively associated with obesity-promoting dietary behaviours and low levels of physical activity in young children [17,18]. Little physical activity trend data during infancy and early childhood is available, however it appears that physical activity levels fall throughout this period [19,20].
In addition to population trend data, there is evidence of tracking of children's dietary [21], sedentary and physical inactivity behaviours [22] from childhood to adolescence and adulthood, which appear to impact on adult health [23]. Thus, the obesity-promoting behaviours learned and supported during these early years may establish lifestyle behaviours that will track throughout the lifespan. Given this, it is reasonable to posit that early childhood provides a unique and circumscribed opportunity within which to establish lifestyle behaviours that will promote health and minimize the risk of the development of obesity.
The role of parents in the promotion of children's behaviours
One of the most powerful predictors of weight management in overweight children is parental involvement, yet there remains an urgent need to examine opportunities to prevent childhood overweight and obesity via parental involvement in the early years [24-26]. Children's eating, physical activity and sedentary behaviours are learnt and sustained in the home and there is evidence that this environment impacts on children's weight [27,28]. Parents have the capacity via their nutrition knowledge, parenting style, modelling and the food environment to impact on children's emerging food choices [27]. Evidence has shown that in a young population (2–6 year olds, n = 564) the strongest predictor of children's fruit and vegetable consumption was parent consumption [29]. In addition, child rejection of fruits and vegetables (negative association) was modifiable with repeated exposure to rejected foods.
In terms of parents' involvement in physical activity with their children, one study reports that parents spend 13% of their child's play time in active play with their infant and that the remainder of time is spent in object play [30]. The use of parks and outdoor spaces is reported by less than half of parents with 5–12 year olds [20]. Children whose parents are active with them are reported to have higher levels of physical activity [31,32]. However, family rules are reported to be inversely associated with children's physical activity [26]. Similarly, rules prohibiting television viewing during mealtimes are reported to be inversely associated with children's television viewing time, and frequency of parent's watching television with their child has been found to be positively associated with children's television viewing [33].
Despite these trends, first-time parents may be particularly receptive to knowledge and skill development around parenting and the promotion of healthy family eating and physical activity behaviours. First-time parents regularly seek advice during their child's first year of life. In Victoria Australia, families make approximately 35 visits to health care providers for their infants during this first year [34]. Importantly, most visits to health service providers are not related to child illness, but rather reflect parental need for support and information during this period of rapid transition. In addition, parents indicate high levels of concern regarding children's appetite, eating patterns and growth, and regularly express the need for more comprehensive guidance in these areas [35]. It is likely that messages delivered to first-time parents may be preferentially received if delivered at times in their child's development when they are actively seeking strategies to manage emerging behaviours, an approach known as anticipatory guidance.
Utilisation of anticipatory guidance
Anticipatory guidance is heralded as a promising approach by which health practitioners might support parents to promote healthy weight in their children by being proactive, informing parents about what to expect and how to manage behaviour, as opposed to supporting parents to manage events after they occur [36-38]. Anticipatory guidance has been shown to be effective across a range of domains, including parent-infant interactions, sleep patterns, injury prevention and reading at home [39].
Despite the promise of anticipatory guidance as an educative approach, just one study utilising this approach in the area of childhood eating has been published [40]. That study involved guidance of parents of new-borns regarding delaying introduction of solids. Compared to controls, the intervention resulted in positive differences in the types of foods introduced and increased confidence in health professionals as primary providers of information.
A randomised-controlled trial targeting overweight indigenous mothers of 1–3 year olds focused on parenting skills to promote improved child eating and physical activity patterns [41]. That study found intervention group infants had decreased relative weight, total energy intake, and improved parent-child interactions around food over 16 weeks. This high quality US study highlights that parents are willing and capable of making positive changes to improve their child's health and body weight.
INFANT: preventing childhood obesity and promoting healthy life-style choices
The INFANT project will employ an anticipatory guidance approach to support first-time parents attending a new parents' group to be skilled in their approaches to their infant's emerging dietary, physical activity and sedentary behaviours. The intervention will be delivered by an experienced dietitian during infants' first 18 months of life at first-time parents groups held within Maternal and Child Health (MCH) centers. Evidence supports the proposition that education regarding lifestyle behaviours is feasible within existing MCH infrastructures and that it is likely to be effective [42,43]. Victoria's 80 MCH Centres (across 39 regions) are a cornerstone of service provision with 96% of all first-time parents attending [34]. MCH nurses routinely establish first-time parents' groups through which education sessions are delivered. A recent prospective study [43] reported that 2/3rds of eligible first-time mothers joined these groups and that of these groups, 2/3rds were still meeting 18 months after the formal sessions had concluded. Drop out from such groups was estimated to be between 10 and 15%. That study also documents the important social environment that first-time mothers' groups provide throughout this early period of parenting. Given the stability of these pre-existing groups and the well-documented capacity of groups to support and reinforce the uptake of knowledge and skills we propose that these groups will provide an important vehicle by which we may deliver an intervention. In addition, our pilot work and engagement with local government areas has demonstrated that access to these groups via MCH nurses is feasible and that willingness of mothers within these groups to participate in research is high.
While this intervention utilises professional support beyond that currently existing in MCH Centres, it remains modest in terms of total cost of implementation and is designed for long-term sustainability, with skills required easily transferable to MCH nurses and other comparable health professionals.
The intervention draws on parenting support theory [44], which emphasizes children's psychological and behavioural goals, logical and natural consequences, mutual respect and encouragement techniques. Emphasis will be placed on parents' understanding of how improved parenting skills can facilitate the development of appropriate eating and activity behaviours in children. In the feeding domain, these approaches have been operationalised by Satter who promotes the 'Division of Responsibility in Feeding' [45] This approach has also been adopted in the US Start Health Feeding Guidelines for Infants and Toddlers [46]. Havery-Berino et al [47] report, in one of the only relevant studies in this age group (age 9 to 36 months), a positive impact on children's dietary intakes using similar approaches.
The intervention will use an anticipatory guidance framework, to coincide with opportunities to support parents regarding feeding, physical activity and sedentary behaviour issues for infants prior to their evolution. In addition, it will utilise the dynamics of existing first time parents' groups to support and reinforce the messages delivered in the intervention.
Aims and Hypotheses
The aim of the study is to test the effectiveness of an early childhood obesity prevention intervention delivered to first-time parents and focussed on parenting skills which support the development of positive diet and physical activity behaviours, and reduced sedentary behaviours in infants from 3 to 18 months of age.
Study hypotheses
In comparison to the control group infants, over the course of the intervention, the intervention group infants will:-
• Demonstrate greater increases in consumption of fruits and vegetables, and smaller increases in consumption of cordials, soft-drinks and juices and energy-dense snack foods.
• Demonstrate greater increases in time spent being physically active and smaller increases in time spent in sedentary behaviours, specifically TV viewing.
• Exhibit reduced incremental BMI gain.
In comparison to the control group parents, the intervention group parents will demonstrate greater increases in:-
• the frequency with which they offer fruit and vegetables, water and milk (rather than cordials, soft-drinks and juices); and smaller increases in the frequency with which they offer energy-dense snack foods to their child;
• knowledge regarding infant eating, physical activity and sedentary behaviours and greater development of positive attitudes/beliefs regarding their capacity to influence these behaviours.
• the adoption of desired feeding strategies, including the division of responsibility in feeding and in providing opportunities for modelling of healthy eating.
• the adoption of strategies, including modelling, for increasing opportunities for physical activity and reducing opportunities for sedentary behaviours.
Design and Methods
Overall study design
The INFANT study is a cluster- randomised controlled trial, with first-time parent groups within local government areas, as the unit of randomization (see Figure 1). The intervention will run from three to 18 months of age (currently funded; National Health and Medical Research Council Grant No. 425801) and additional funding will be sought for follow-up to assess sustainability of outcomes. Ethical approval to conduct the study has been granted by the Deakin University Ethics Committee (ID number:EC 175-2007) and by the Victorian Office for Children (Ref : CDF/07/1138).
Figure 1. Study design.
Participants and recruitment
A two-stage random sampling process will be used to select first-time parent groups. At the first stage, twelve local government areas within a 60 km radius of the research centre (Deakin University in Burwood, Victoria, Australia) will be randomly selected. Local government areas within this geographical area that have an annual birth rate lower than 600 will be excluded. At the second stage, first-time parent groups within selected local government areas will be randomly selected, proportional to the total number of first-time parent groups within each area. The first-time parents group currently underway will then be invited to participate. These first-time parent groups will be accessed initially via the MCH nurse who will set up an appropriate time to invite a member of the research team to speak with the group about the study. This team member will explain the study to the group and distribute research information packages. The packages will contain general study information, consent forms and contact details of the research team so any parent is free to contact the team to discuss any concerns or unanswered questions. A majority of group members will be required to consent to allow the group to participate in the study. Non-consenting parents within participating groups will be permitted to attend the intervention sessions, but will not be required to provide data or be contacted by the research team in any other way.
Inclusion criteria
Parents will be eligible to participate if they are able to freely give informed consent, are first-time parents, members of a participating 'first-time parents group' and are able to communicate in English.
Exclusion criteria
Parents will be excluded from the study if they are unable to give informed consent or are unable to communicate in English. Infants with chronic health problems that are likely to influence height, weight, levels of physical activity or eating habits will be excluded from analyses but will be permitted to participate in the study.
Sample size
A sample of 600 first time parents participating in first-time parents' groups (300 in each arm) will be recruited for the study. The sample size calculation is based on detecting changes in one of the main outcomes: dietary intake. The authors are not aware of any data providing means and standard deviations on physical activity, sedentary behaviours or body mass index in this age group. Consequently, sample size calculations were undertaken for dietary outcomes using three day weighed food data on 18 month old Australian children [13,48].
As there are no quantitative dietary recommendations for children less than four years old in Australia, we suggest a 25% increase in vegetable consumption as a minimum target on which the sample size calculations are based. Australian data show that 18-month old children eat around 32 grams of vegetables (not including potato) per day with a standard deviation of 15 g [48]. To detect an increase in vegetable consumption as small as 25% the total number of subjects required is 112 (56 in each arm). To account for within-group clustering (resulting from randomisation at the first- time parent group level) the sample size was increased by the design effect/inflation factor of 2.8, based on assumptions of each cluster consisting of approximately ten people and a conservative inter-class cluster coefficient of 0.2. The sample size estimation was further adjusted to account for attrition (40%) with the potential of loss of entire groups to follow-up and we plan to over sample by 15%. Thus the final sample is 600 (300 in each arm).
Randomization
First-time parents groups will be randomised after recruitment in order to ensure baseline equivalence and minimise selection bias. Within each local government area, first-time parents groups will be randomly allocated to the intervention or control group in order of recruitment, using a computer generated random number schedule developed by a statistician who has no contact with the centres. Prior to the first intervention session families will be informed by letter regarding the outcome of randomisation.
Intervention group
The intervention will be delivered by a dietitian and is comprised of six sessions delivered at three month intervals during the regular meeting time of the first-time parents' group (see Table 1). Based on an anticipatory guidance framework the intervention will incorporate a range of modes of delivery and educational strategies including brief didactic sessions, use of group discussion and peer support, exploration of perceived barriers, use of visual and written messages, follow-up delivery of messages by text-messaging and mail-outs. All educational concepts will be developed iteratively, that is, messages will be repeated and expanded upon over the course of the intervention.
Table 1. Intervention time-frame and focus
Control group
The control group families will receive usual care from their MCH nurse. In addition, these families will be sent general health newsletters (e.g. dental health, sun protective behaviours, general safety), and will receive Birthday and Christmas cards. These families' participation will be rewarded with gifts (to a maximum value of $15.00) on receipt of completed questionnaires.
Measures
Parent and infant data will be collected using parent self-completion questionnaires, apart from infant dietary intake data which will be collected by telephone interview. As outlined in Table 2, all data (appropriate to the age of the child) will be collected every three months, corresponding with the six intervention sessions. Repeated data collection is necessary given the rapid changes in height, weight, eating and activity behaviours in infants. The measures collected are detailed below.
Table 2. Measures and time-frame for the study
Dietary intake
Dietary intake for mother and father will be assessed using The Cancer Council's Dietary Questionnaire for Epidemiological Studies (Version 3) at baseline and study conclusion. This questionnaire is an updated version of the semi-quantitative food frequency questionnaire specifically developed for the Melbourne Collaborative Cohort Study [49]. Child's dietary intake will be assessed by telephone-administered multi-pass 24-hour recall with parents [50]. Visual aids will be provided to primary carers in advance of interviews to help in the estimation of quantities of food consumed. Three days of dietary data will be collected (including one weekend day) when the infant is 9 and 18 months of age.
Physical activity
Parents will report their frequency and duration in physical activity during the previous week using the Active Australia Survey [51]. In addition, at 12 and 18 months parents will be asked to report the number of hours their child typically spends playing outdoors on weekdays and weekend days.
Sedentary behaviors
Parents will be asked the amount of time the infant spends watching television on a typical weekday and on a typical weekend day [52], and to estimate the amount of time each day that the child spends immobile. Parents will also report the total time they spend watching television during their leisure-time in a typical week [53].
Home food environment
Three aspects of the home food environment will be assessed. Aspects of nutrition knowledge focused around nutrition targets of the intervention will be assessed modified subscales of the validated Nutrition Knowledge Questionnaire [54], Parent Feeding Style will be assess using the Child Feeding Questionnaire (CFQ) [55], the Caregivers Feeding Style Questionnaire CFSQ [56].
Family physical activity and sedentary environment
Parents will be asked general questions relating to their knowledge about physical activity in early childhood, their interactions with their child around physical activity and an audit checklist on the physical activity and sedentary home environment.
Standard demographic and socio-economic information will be collected by parental report. Anthropometric measures (height/length and weight) on the infant and parents will be collected by trained staff.
Data analysis
All analyses will be conducted using the intention to treat principle. Generalized Estimating Equations (GEE) [57] will be used to fit regression models to describe the effects of the intervention on key outcome variables among parents and infants. Separate models will be fitted, to determine differences in key outcome variables in the intervention and control groups.
Discussion
The prevalence of obesity in early childhood is rapidly increasing and is determined, in part, by eating, physical activity and sedentary behaviours. These behaviors are predominantly learnt at home in the first five years of life, and impact upon health throughout life. Given this, the early years hold promise as a time when obesity prevention may be most effective. However, research in this early period of life is lacking. This cluster-randomized trial will be one of the first to investigate whether a health promotion program delivered to first-time parents in their usual social settings can promote healthy eating, physical activity and reduced sedentary behaviours in infants. If effective, this program could protect children from the development of obesity and its associated social and economic costs. Further this study has the capacity to substantially strengthen our understanding of strategies that will promote health among families and may result in policy change both nationally and internationally.
Competing interests
The author(s) declare that they have no competing interests.
Authors' contributions
KC took the lead in writing and designing the study subsequently funded by a National Health and Medical Research Council Grant. She has also assisted with the modification of this grant for publication.
KH contributed to the overall concept and design of the study and assisted with the writing of the grant and its modification for publication.
DC, KB, JS, ZM provided expert input and support overall for the writing of this grant with particular emphasis on design, measures of physical activity and statistical analyses.
All authors read and approved the final manuscript.
Acknowledgements
We would like to acknowledge the dedication shown by our colleague Natasha Napiza who has worked hard to transform the INFANT grant into a document suitable for publication. We would also like to thank our colleague Dr Sarah McNaughton for her considerable input into the decisions about most appropriate dietary methodologies and to Lisa Gold for her advice and support regarding the design of the economic evaluation of this program. This study has been funded by the Australian National Health and Medical Research Council (425801).
References
1. World Health Organisation: Obesity: preventing and managing the global epidemic : Report of the WHO consultation. In Book Obesity: preventing and managing the global epidemic : Report of the WHO consultation. (Editor ed.^eds.). City: World Health Organisation; 1999. 
2. Lobstein T, Baur L, Uauy R, TaskForce. IIO: Obesity in children and young people: a crisis in public health.
Obes Rev 2004, 5:4-104. PubMed Abstract | Publisher Full Text
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