This chapter examines several issues on obesity in early childhood that have direct practical relevance to supporting healthy weight gain in this critical period of life. The first fundamental issue for child health nursing practice is the definition of normal growth in early childhood, which leads directly into an examination of the assessment of at-risk growth patterns and other risk factors for later childhood (and adult) obesity. Appropriate feeding practices are fundamental to healthy weight gain in early childhood and these recommendations are reviewed as well as the importance of active play, motor skill development and reduced television viewing time. Patterns for all human behaviors are highly influenced by environments, and this is most true in the early childhood years. Thus, the many preschool settings outside the home environment are also examined as opportunities for implementing the policies and practices needed to promote healthy eating and active play.

Historically, good health and nutrition in childhood have been defined by the capacity to support normal growth. Existing national and international standards have defined normal growth based on the weight and length gain observed in apparently “healthy” children. This has led in practice to support the notion that “bigger is better”. This is a reasonable approach if the objective is to enhance survival in infancy and early childhood in areas where malnutrition and infection in synergy claim the lives of infants and young children. However, it is certainly not the case in countries where deaths of young children are rare and the concern has shifted to the prevention of obesity and related burden of chronic disease.¹ Moreover, there is also mounting evidence that exposure to undernutrition during early life (i.e. in utero and the first two years of life) may have long-term consequences for adult body composition and health if there is a mismatch between early nutritional deprivation and later nutritional conditions that may support rapid weight gain in childhood. ^2–4 Thus, the definition of “normal” growth is of paramount importance to secure normal health and nutrition of both individuals and populations in developed and developing countries.

Growth references and standards to define growth in early childhood

The reference/standards used to assess growth are fundamental for both clinical practice and to establish public health recommendations. Normative gender and age specific data of weight, height, weight/height, and BMI have been used as indicators of nutritional adequacy in infancy, childhood and adolescence.

Most of the available growth charts are based on the observed growth for a normal reference population rather than recommended growth based on health outcomes throughout the life course. Until 2006, the growth charts most commonly used were based on the USA National Center for Health Statistics (NCHS) The NCHS growth reference, which originally served as the basis for the WHO international growth standards for infants aged 0–36 months, was derived from children growing in an affluent rural society in the town of Yellow Springs, Ohio.² However, these references had major flaws because they were derived from a non-representative sample of the population and the infants included were predominantly formula fed and received energy-dense complementary foods. Thus, the NCHS distributions of normal weight-for-age and weight-for-length are skewed towards higher values, relative to those observed in predominantly breastfed infants and this may have been a contributory factor to the increase in childhood obesity, since normal-sized children may have been considered underweight and prescribed additional energy.

Aware of these limitations, in 2006 the WHO launched the Multi-country (Brazil, Norway, India, Ghana, USA and Oman) Growth Reference Standard (MGRS). The MGRS was developed based on the growth of infants and children from diverse geographical regions, whose mothers were non-smokers of middle to high income so that environmental conditions were not restrictive for growth, and care givers followed the established WHO feeding recommendations (i.e. infants were predominantly breastfed for 4–6 months and fed appropriate complementary foods after weaning).³ The new international growth reference provides a scientifically reliable descriptor of physiologic growth and a powerful tool for advocacy in support of good health and nutrition. Most importantly, this reference is based on the growth of the breastfed infant as the normative standard.

Definitions of overweight and obesity in children

In children, there is a lack of consistency in the use of the terms “overweight” and “obesity”. All recommendations take into account two levels of excess weight, but use of different definitions and terminology may lead to confusion in interpreting results and comparing prevalence across populations. This is further complicated by the lack of evidence on the most appropriate anthropometric indices and cut-off points that best predict long-term adverse health outcomes. BMI has been used to define categories of excess weight so that there is concordance with adult assessment, although for children the definitions are age and sex specific. The 2000 CDC growth charts provide BMI-for-age curves for the US population over 2 years of age⁴ and define children with a BMI ≥ 95th percentile as “overweight” and children with BMI between the 85th and the 95th percentile as “at risk of over-weight”.⁵ The WHO growth standards for 0–5-year-olds in combination with the new WHO reference for 5–18-year-olds provide an international reference from birth to 18 years.⁶ The terminology for body size categories (thinness, normal weight, overweight, obesity) using the WHO and International Obesity Task Force charts ensures concordance between adults and children because the childhood BMI curves were anchored at age 18 years to the agreed adult cut-off points (18.5, 25, 30 kg/m² for thinness, overweight and obesity respectively). ^7,8

The relationship between low birth weight and the later occurrence of obesity and central obesity has been documented in a number of epidemiological studies conducted mostly in industrialized countries,^9,10 and in follow-up studies of historic cohorts from transitional countries.¹¹ In most developing regions low birth weight, and underweight and stunting in young children, coexists with overweight and obesity in older children, adolescents and the adult population;¹² thus, it is likely that the effect of low birth weight in these countries will be higher than that of developed countries. Analyses of the five existing cohort studies from developing countries (India, Guatemala, South Africa, Brazil and the Philippines) have reported that in India, Guatemala and Brazil, birth weight was positively associated with BMI at age 25–30, yet the associations were stronger for lean mass than for fat mass.¹¹

Macrosomia or high birth weight (greater than 4,000 g) is also a potential problem with long-term consequences. Excessive intrauterine growth in this case is driven by elevated maternal glucose and insulin levels due to gestational diabetes and/or maternal overweight.¹³ Several studies of macrosomic children have shown that high birth weight is a risk factor for later development of obesity and diabetes.^14–17

The importance of the existence and timing of a period of rapid childhood growth in potentiating the relationship between fetal undernutrition and later obesity is a matter of current debate,^18,19 partly because of the rapid changes in the environment associated with progressive increase in the prevalence of obesity. Older cohorts have subtle changes. The systematic review by Monteiro and Victora²⁰ identified 16 studies that presented data on the role of rapid childhood growth as a possible determinant of obesity in adulthood, 13 of which reported significant associations, although they also noted the significant lack of standardization between studies making interpretation difficult. The degree to which rapid infant growth represents a risk may depend on whether it occurs in the context of recovery from fetal growth restriction and results in normalization of body weight and length, or whether excess growth is predominantly ponderal with constrained linear gain, thus leading to excess weight for length.^11,21

The effect of rapid weight gain in early life may also depend on prenatal and postnatal characteristics such as exposure to tobacco in utero, maternal overweight or obesity, the type of early feeding, or the amount of fat in the diet.^22,23 Overall, the effect of rapid infant weight gain on later development of overweight seems to be relevant. In relatively contemporary cohorts of children from USA it has been reported that the population risk for overweight at 4 or 7 years attributable to infant weight gain (0 to 4–6 months) in the highest quintile is around 20%.^24,25 Another study in a non-contemporary cohort of African-Americans reported that almost 30% of the risk of overweight at 20 years was due to a rapid weight gain (over one standard deviation above the mean value) from 0 to 4 months of age.²⁶ Given the actual increase in obesity among children and adults, is likely that the attributable risk might even be higher.

The age at adiposity rebound (age at which the BMI increases after its nadir in early childhood) is another period in which childhood growth seems to be critical for later obesity.²⁷ On average, this normally happens between the ages of 5 and 7 but it has been shown that an earlier adiposity rebound is associated with increased fatness later in life.²⁸ For example, one study reported that adults who had their adiposity rebound by 4.8 years had a 6 times higher risk of having a BMI > 27 kg/m² than adults who had their adiposity rebound after 6.2 years.²⁹ There remains some uncertainty, however, over whether the apparent negative effect of an early adiposity rebound is independent of early life BMI or BMI percentile crossing.^30,31

Recommended energy intakes

Energy recommendations for infants and children published by FAO/WHO/UNU in 2004 are based on actual measurements and estimates of total daily energy expenditure, either by the doubly labeled water method or estimates based on heart rate monitoring during active periods coupled to individual calibrations of oxygen consumption ³² The energy needs for tissue deposition related to growth in case of infants, children and adolescents were added to the estimate of daily energy expenditure. The recommendations also include a need for physical activity to maintain fitness and health, and to reduce the risk of developing obesity and diseases associated with sedentary lifestyles. Moreover, different requirements are given for populations with lifestyles that involve different levels of habitual physical activity, starting at 6 years of age.

In the case of infants, the new recommendations are based on breastfed infants rather than those who are formula fed; for the first year of life the mean values for the former are 5–10% lower than figures for formula-fed babies. The present recommendations based on expenditure are also substantially lower for children up to age 10 years in comparison to those derived on observed food intake as used in 1985 by FAO/WHO/UNU.

Breastfeeding

The new recommendations will serve to strongly support exclusive breastfeeding since, as energy needs drop, the sufficiency of breast milk energy supply is prolonged. Recent meta-analyses of published observational studies have suggested that breastfeeding is associated with a lower prevalence of obesity³³ and BMI later in life³⁴ in a dose-dependent way (i.e. longer duration of breastfeeding is associated with lower risk of overweight).³⁵ The mechanisms by which breast-feeding would decrease the risk of obesity could be broadly summarized in three categories: nutritional components of milk; growth pattern of breastfed babies; and behavioral. There is some concern that the association between breastfeeding and obesity may not be causal but confounded by unmeasured factors, ^36,37 and the only available randomized controlled trial based on an intervention to promote exclusive and prolonged breastfeeding showed that the intervention increased duration and exclusivity of breastfeeding but did not reduce adiposity at age 6.5 years.³⁸

Other early life-risk factors for obesity

A number of other potential early life predictors of obesity have been identified in studies conducted mainly in developed countries. The most consistent associations point to a role of maternal overweight, maternal feeding behaviors, low physical activity levels, low socio-economic status, and obesogenic environments.³⁹

Physical activity

Physical activity in childhood years has been identified as a key factor in the prevention and control of over-weight and obesity.^40–48 Benefits include improvement in children’s general health status, their ability to maintain normal growth and development, and delay prevent the onset of obesity.^49,50 Evidence shows that patterns of physical activity established early can carry over into adulthood^49,51 and a positive relationship has been shown between being physically active during preschool years and lower weight gain by early adolescence,⁴¹ confirming the importance of the early years. Additional benefits of physical activity during childhood are enhanced psychological well-being, self-esteem, moral and social development, developing an active lifestyle and decreasing the prevalence of chronic disease factors.⁵²

Physical activity for children may be planned (structured) or incidental (unstructured). The activity of day-to-day living can be described as unstructured, whereas structured activities include more formal sporting games and activities.^49,50,53 Although young children have a natural tendency to be somewhat physically active, there is evidence to show that over recent decades, children have become less so.^50–52

Physical activity is important for maintaining normal growth and development during childhood and adolescence⁵⁰ and the 2005 US national physical activity guidelines for preschool-aged children recommended at least two hours of physical activity a day, half in structured physical activity and half in unstructured, free play settings.⁵⁴

Play is the “spontaneous activity in which children engage to amuse and occupy themselves” and is critically important for preschool children.⁵⁵ Movement and activity can satisfy a child’s curiosity, promote good feelings and happiness, enhance problem-solving skills and assist in developing lifelong attitudes towards physical activity.⁵⁶ Children are also able to gain success through activity challenges and enhance social interaction through games and activities. Learning and mastering the fundamental motor skills (FMS) in early childhood, has a positive effect on involvement in physical activity such as organized sports later in life.⁵⁷ And a positive reinforcer for increasing participation in physical activity has been shown to be successful motor performance.⁵⁸

To ensure that young children participate sufficiently, physical activities need to be well integrated into children’s daily routines.⁵⁹ The activities should promote the necessary skills to facilitate enjoyment and enable children to develop an appreciation of physical movement, which will most likely track through adolescence and into adulthood. One way to ensure that children in day care settings engage in adequate physical activity is to add structured play to their daily program as well as providing more time for free play in environments which facilitate physical activity.⁶⁰

Physical inactivity

The development of childhood obesity is complicated and multi-factorial, however, screen time has been identified as an independent modifiable risk factor for the development of childhood obesity,^61–65 with high amounts of screen time associated with less physical activity and higher child BMI.^61,63–65

The American Academy of Pediatrics recommends no television viewing for children under the age of 2 years, and that children older than 2 years watch no more than 1–2 hours of TV and video per day. ^66,67 It has been shown that preschoolers who watch more than 3 hours of TV/day are 50% more likely to become obese than children who watch <2 hours/day⁶⁸ and 3 main mechanisms by which TV impacts weight gain have been proposed:⁶⁹

1. TV displaces time spent doing physical activity.

2. TV promotes in-between meal snacking, thus increasing daily caloric intake.

3. TV food advertising influences children’s food choice, attitudes and beliefs.

A recent study of children in the USA has shown that two thirds of the children aged under 2 years, and over 80% of 3–4-year-olds watched television on a typical day. On that typical day, the average time spent watching television by children of all ages was 1 hour and 19 minutes. In addition, approximately one third of the children watched videos or DVDs on a typical day, for an average of 1 hour and 18 minutes.⁷⁰ About one fifth of 0–2-year-olds and more than one third of the 3–4-year-olds and the 5–6-year-olds also had a television in their bedroom, which was related to higher levels of viewing, most notably for the youngest age group.⁷⁰

Child care settings

The ecological model has been utilized to examine the range of influences that alter the ability of children to maintain a healthy weight.⁷¹ In addition to the home, child care settings are recognized as important environments that can have an impact on children’s weight through the nutritional quality of the foods provided and children’s access to opportunities for physical activity while in day care.

The proportion of mothers returning to the work-force before their children reach school age is increasing and children are going into child care at younger ages. Therefore, child care arrangements (either outside their own homes or by others within their homes) are becoming increasingly important settings for child development.

Early childhood settings and services vary widely around the world as shown in a comprehensive review of child care services across 29 countries in 1993.⁷² Although the terminology varies, common types of formal care can be summarized. Day care centers (also sometimes known as crèche or nursery) provide up to a full day of care for groups of children in a non-residential setting such as a business, church or school. Family day care (also known as family- or home-based care) provides a full day of care for small groups of children (usually up to six) in the care provider’s home, or a large family of group child care homes usually have two care providers caring for seven to twelve children in a provider’s home. Home care is typically provided by a non-relative such as a nanny or au pair in the family home and informal (or “kith and kin”) care is provided by a relative, neighbor, friend or babysitter.^72,73

Parents, therefore, choose from a range of child care options and some countries have day care systems dominated by family day care, whereas other countries emphasize center-based care. Children can enter day care from six weeks of age and can be in care for up to 40 hours per week until they reach school age. A study in the USA found that 18% of preschool children were not in child care, 16% were in care for 1 to 14 hours per week, 25% for 15 to 34 hours per week and 41% for 35 hours or more per week.⁷⁴ Across the USA, approximately 80% of children aged under 5 years who had working mothers were found to be in a child care arrangement (both formal and informal) for about 40 hours per week. ⁷³

Similarly, in Australia, the predominant types of formal care are center-based long day care and family day care. A recent study has shown that the use of formal child care has increased from about 15% in 1966 to about 23% in 2005. In 2005 the usage of formal care increased from 7% for children up to 12 months, to 31% at the age of 1 year, and 53% for children aged up to 3 years.⁷⁵ Of all children aged 0–12 in the survey who used formal care, about half were in care for 10 hours or less and about 30% were in care for 10 to 20 hours.

The increased participation of women in the labor force and the increased number of children with both parents working is viewed as a major change in family life over the last thirty years.⁷⁶ In recent years there has been a paradigm shift from a view that child care is an exclusively family responsibility to acceptance of a shared responsibility and recognition that a significant proportion of the child raising process is now a public concern. This paradigm shift is seen as the legitimization of out-of-home child socialization. It necessitates an effectively integrated early childhood education and care system and the concept of extra-familial care and education as shared family and state responsibility.⁷²

Child care and obesity risk

A study on the effect of maternal employment on childhood obesity demonstrated that a 10-hour increase in average hours worked per week over a child’s lifetime increased the probability of childhood obesity by 1 percentage point⁷⁷ Although the mechanisms are unclear, it appears that the relationship is dependent more on the intensity of work rather than working per se. Women who work less intensive hours may also have time to participate in active play with their child, prepare nutritious meals, walk to/from school with their child and even have higher breast-feeding rates and duration—all factors thought to be related to a child’s risk of being overweight or obese.⁷⁶

Despite the increasing usage of formal care for young children, insufficient attention has been paid to the relationship between child care and childhood obesity.^71,73 The nutrition and physical activity environments in child care settings have not been extensively studied, and the little evidence that does exist indicates that the meals provided are often nutritionally inadequate and the level of physical activity by children in day care may also be insufficient.

The food environments in early childhood settings

It has been suggested that young children attending day care may have less adult modeling and encouragement for eating healthier foods, as well as less control on portion sizes, than children receiving individual attention.⁷⁸ It is also known that as children spend more time in child care, maternal influence on children’s diet diminishes and other care givers play a more critical role in children’s nutrition.⁷⁹ This represents a missed opportunity to promote healthy weight in young children.

In the USA, between 1977 and 1998 the diet of preschool children (3–5 years) increased in the consumption of added sugars, juices and total energy.⁸⁰ In the case of infants and toddlers (4–24 months) energy intakes were higher than recommended, up to a third of children ate no vegetables or fruit on the day of the dietary recall, and, for children 15 to 18 months, the vegetable most commonly eaten was French fries.⁸¹

Energy, macronutrient and micronutrient contents of the diets provided at day cares should be based on daily recommendations for each age and the FAO 2004 energy recommendations,³² depending on the amount of waking hours that children expend in the day care. However, the acceptability of the food offered at the day cares should be considered when trying to achieve these dietary recommendations. Also, attention should be paid to feeding practices of child care providers because they have a direct impact on the development of eating behaviors of preschool children⁸² which, in turn, may be related to later obesity.⁸³

For children below 6 months, exclusive breastfeeding should be recommended followed by mixed breastfeeding until at least 12 months.⁸⁴ Day care centers should ensure that working mothers have a supportive breastfeeding environment (e.g. availability of breast pumps at the centers, a place for mothers to breastfeed, adequate breast milk storage). Appropriate content of vitamins and minerals of weaning foods provided at the day care should be ensured without exceeding energy, protein and fat recommendations. Examples of interventions conducted in early childhood settings are provided in Chapter 8.

The physical activity environments in early childhood settings

Environments are a major contributing factor to children’s physical activity participation and facilities, equipment and the amount and type of physical space all have the potential to influence a child’s engagement in physical activity.^53,59 In early childhood settings it is important that children have access to sufficient indoor and outdoor space to move about freely, enabling them to use their bodies actively. Children’s physical activity participation has been shown to increase with participation in outdoor activities.⁸⁵

Children who spend significant time in day care and kindergarten settings may have their participation in physical activity limited or enhanced largely by the setting’s inclusion of physical activity in the program. A reduction in children’s free playtime between 1981 and 1997 has been associated with an increase in the amount of time children spend in structured settings such as school and day care.⁸⁶ Brown et al conducted a study on the amount of physical activity that American children participated in during preschool attendance. This study found that 80% of the children’s time was spent on sedentary activities (e.g. transition, snack and nap time) and only 5% in moderate to vigorous physical activity.⁸⁷ This indicates a need to enhance opportunities for children to be active, which includes evaluating the amount of time allocated to free and structured physical activity/play in care settings. A recent study found that children in child care centers with supportive physical environments achieved higher participation in moderate to vigorous physical activity, spent less time in sedentary activities and had higher average physical activity levels when compared to less supportive centers.⁸⁸

As so many young children attend child care, these settings can be a major influence in shaping children’s physical activity participation and, therefore, contribute to combating the childhood obesity epidemic.^73,89 Early childhood staff who work in long day care settings have a unique opportunity to encourage and facilitate an active lifestyle among children. Engaging with these workers to develop solutions to overcoming barriers in care settings will be important before sustainable changes can be implemented.

The new WHO standards for growth have been a major step forward in creating credible reference standards for normal growth and definitions of obesity, overweight and thinness. This will strengthen the emerging evidence on the growth-related risk factors for future obesity. There are also continuing improvements in the standards and recommendations for energy intake, physical activity and sedentary behaviors for early childhood. The existing patterns of breastfeeding, dietary intake, active play and television viewing in preschool children suggest that there are major opportunities for shifting towards healthier and less obesogenic patterns of these behaviors. While the home environment is paramount for promoting these healthy behaviors, the increasing use of child care provides an excellent opportunity for those settings to take a leading role to model healthy eating and active play in this critically important age group.

1 Popkin BM, Gordon-Larsen P: The nutrition transition: worldwide obesity dynamics and their determinants. Int J Obes Relat Metab Disord 2004; 28(Suppl. 3):S2–S9.

2 Working Group on Infant Growth: An evaluation of infant growth: the use and interpretation of anthropometry in infants. WHO Bull World Health Organ 1995; 73(2): 165–174.

3 de Onis M, Garza C, Victora CG, Onyango AW, Frongillo EA, Martines J: The WHO Multicentre Growth Reference Study: planning, study design, and methodology. Food Nutr Bull 2004; 25(1 Suppl.):S15–S26.

4 Kuczmarski RJ, Ogden CL, Grummer-Strawn LM et al: CDC growth charts: United States. Adv Data 2000; 8(314):1–27.

5 Must A, Dallal GE, Dietz WH: Reference data for obesity: 85th and 95th percentiles of body mass index (wt/ht2) and triceps skinfold thickness. Am J Clin Nutr 1991; 53(4): 839–846.