8.1 Body Changes

In early childhood as in infancy, the body and brain develop according to powerful epigenetic forces, biologically driven and socially guided, experience-expectant and experience-dependent. [Lifespan Link: Experience-expectant and experience-dependent brain development are explained in Chapter 5.] Bodies and brains mature in size and function.

Growth Patterns

Compare a toddling, unsteady 1-year-old with a cartwheeling 6-year-old. Body differences are obvious. During early childhood, children slim down as the lower body lengthens and fat turns to muscle.

In fact, the average body mass index (BMI, the ratio of weight to height) is lower at ages 5 and 6 than at any other time of life. Gone are the infant’s protruding belly, round face, short limbs, and large head. The center of gravity moves from the breast to the belly, enabling cartwheels, somersaults, and many other motor skills. The joys of dancing, gymnastics, and pumping a swing become possible; changing proportions enable new achievements. [Lifespan Link: Body mass index is discussed in Chapter 11.]

Size and Balance These cousins are only four years apart, but note the doubling in leg length and marked improvement in balance. The 2-year-old needs to plant both legs on the sand, while the 6-year-old cavorts on one foot.

KATRINA WITTKAMP/GETTY IMAGES

Increases in weight and height are apparent as well. Over each year of early childhood, well-nourished children gain about 4½ pounds (2 kilograms) and grow almost 3 inches (about 7 centimeters). By age 6, the average child in a developed nation:

• Weighs between 40 and 50 pounds (between 18 and 22 kilograms)
• Is at least 3½ feet tall (more than 100 centimeters)
• Looks lean, not chubby (ages 5 to 6 are lowest in body fat)
• Has adult-like body proportions (legs constitute about half the total height)

When many ethnic groups live together in a nation with abundant food and adequate medical care, children of African descent tend to be tallest, followed by those of European descent, then Asians, and then Latinos. However, height differences are greater within ethnic groups than between groups, evidence again that ethnicity is not determined by genes.

Nutrition

Although they rarely starve, preschool children sometimes suffer from poor nutrition. The main reason for preschool malnourishment in developed nations is that too often young children’s small appetites are satiated with unhealthy foods, crowding out needed vitamins.

Adults often encourage children to eat, protecting them against famine that was common a century ago. Unfortunately, that encouragement is destructive when food is abundant. This is true in many nations: In Brazil 30 years ago, the most common nutritional problem was undernutrition; now it is overnutrition (Monteiro et al., 2004), with low-income Brazilians particularly vulnerable (Monteiro et al., 2007).

Victory! He’s on his way. This boy participates in a British effort to combat childhood obesity; mother and son exercising in Liverpool Park is part of the solution. Harder to implement are dietary changes—many parents let children eat as much as they want.

HOWARD BARLOW/ALAMY

A detailed study of 2- to 4-year-olds in low-income families in New York City found many overweight children, with an increase in weight as family income fell (J. A. Nelson et al., 2004) and as children grew older (14 percent at age 2; 27 percent at age 4). This age pattern suggests that eating habits, not genes, were the cause. In that New York study, overweight children were more often of Hispanic (27 percent) or Asian American (22 percent) descent rather than of African (14 percent) or European (11 percent) descent.

One explanation for North American ethnic differences is that many low-income children live with grandmothers who knew firsthand the dangers of malnutrition. Indeed, immigrant Latino and Asian American grandparents are unlikely to be obese themselves but often have overweight grandchildren (Bates et al., 2008). For every ethnic group, the reality of food availability for young children has changed faster than traditions have.

Overfed children often become overweight adults. An article in The Lancet (the leading medical journal in England) predicted that by 2020, 228 million adults worldwide will have diabetes (more in India than in any other nation) as a result of unhealthy eating habits acquired in childhood. This article suggests that measures to reduce childhood overeating in the United States have been inadequate and that “U.S. children could become the first generation in more than a century to have shorter life spans than their parents if current trends of excessive weight and obesity continue” (Devi 2008, p. 105).

Appetite decreases between ages 2 and 6 because young children need fewer calories per pound than they did as infants. This is especially true for the current generation since children get much less exercise than former generations did. They do not tend the farm animals, walk long distances to school, or even play outside for hours. However, instead of accepting this generational change, many of the older generations fret, threaten, and cajole children to overeat (“Eat all your dinner and you can have ice cream”). Pediatricians have found that most parents of infants, toddlers, and preschoolers believe that relatively thin children are less healthy than relatively heavy ones, a false belief that leads to overfeeding (Laraway et al., 2010).

Although most children in developed nations consume more than enough calories, they do not always obtain adequate iron, zinc, and calcium. For example, children now drink less milk than formerly, which means less calcium and weaker bones later on. Another problem is sugar. Many customs entice children to eat sweets—in birthday cake, holiday candy, desserts, and other treats.

Sweetened cereals and drinks (advertised as containing 100 percent of daily vitamins) are a poor substitute for a balanced, varied diet, partly because some nutrients have not yet been identified, much less listed on food labels. The lack of micronutrients is severe in poor nations, but vitamin pills and added supplements do not always help (Ramakrishnan et al., 2011).

Eating a wide variety of fresh foods may therefore be essential for optimal health. Compared with the average child, those preschoolers who eat more dark-green and orange vegetables and less fried food benefit in many ways. They gain bone mass but not fat, according to a study that controlled for other factors that might correlate with body fat, such as gender (girls have more), ethnicity (people of some ethnic groups are genetically thinner), and income (poor children have worse diets) (Wosje et al., 2010).

An added complication is that an estimated 3 to 8 percent of all young children are allergic to a specific food—and almost always a common, healthy food: Cow’s milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish are the usual culprits. Diagnostic standards vary (which explains the range of estimates), and treatment varies even more (Chafen et al., 2010).

Some experts advocate total avoidance of the offending food—there are peanut-free schools, where no one is allowed to bring a peanut butter sandwich for lunch—but other experts suggest that tolerance should be gradually increased, beginning by giving babies a tiny bit of peanut butter (Reche et al., 2011). Fortunately, many childhood food allergies are outgrown, but since young children are already at nutritional risk, allergies make a balanced diet even harder.

Eat Your Veggies On their own, children do not always eat wisely.

VAHAN SHIRVANIAN/CARTOONSTOCK.COM

Too much sugar and too little fiber cause tooth decay, the most common disease of young children in developed nations. More than one-third of all U.S. children under age 6 already have at least one cavity (Brickhouse et al., 2008). Sugary fruit drinks and soda are prime causes, and sugar-free soda contains acid that makes decay more likely (Holtzman, 2009).

Fortunately, “baby” teeth are replaced naturally at about ages 6 to 10. The schedule is primarily genetic, with girls averaging a few months ahead of boys. However, tooth care should not be postponed until the permanent teeth erupt. Severe tooth decay in early childhood harms those permanent teeth (which form below the first teeth) and can cause jaw malformation, chewing difficulties, and speech problems.

Teeth are affected by diet and illness, which means that the state of a young child’s teeth can alert adults to other health problems. The process works in reverse as well: infected teeth can affect the rest of the child’s body.

Most preschoolers visit the dentist if they have U.S.-born, middle-class parents, However, the less education parents have, the less likely they are to know the importance of early dental care (Horowitz et al., 2013). Many young and low-income parents are overwhelmed with work and child care and do not realize that tooth-brushing is a vital habit, best learned early in life (Mofidi et al., 2009; Niji et al., 2010).

If the parent was raised in a nation with inadequate dental care (sometimes visible in the number of toothless elders), they may not get dental care for their children. However, in many countries, ignorance is not the problem; access and income are. In the United States, free dentistry is not available to most poor parents, who “want to do better” for their children’s teeth than they did for their own (Lewis et al., 2010).

Hazards of “Just Right”

Young Children’s Insistence on Routine This chart shows the average scores of children (who are rated by their parents) on a survey indicating the child’s desire to have certain things—including food selection and preparation—done “just right.” Such strong preferences for rigid routines tend to fade by age 6.

Many young children are compulsive about their daily routines, insisting that bedtime be preceded by tooth-brushing, a book, and prayers—or by a snack, sitting on the toilet, and a song. Whatever the routine, children expect it and are upset if someone puts them to bed without it. Similarly, mealtime can become a time for certain foods, prepared and placed in a particular way, on a specific plate.

The early childhood wish for routines, known as the “just right” or “just so” phenomenon, might signify an obsessive-compulsive disorder in older children. For that reason, adults should help older children reduce their anxiety (Flessner et al., 2011). However, among young children, a wish for continuity and sameness is normal and widespread (Evans et al., 2006; Pietrefesa & Evans, 2007). As a team of experts explains: “Most, if not all, children exhibit normal age-dependent obsessive-compulsive behaviors [that are] usually gone by middle childhood” (March et al., 2004, p. 216).

Overeating can become a serious problem: Indulgence and patience for “just right” becomes destructive if the result is an overweight child. [Lifespan Link: Obesity is discussed in detail in Chapter 11, and Chapter 20.]

Pediatricians need to provide parents of 2- to 5-year-olds with “anticipatory guidance” (Collins et al., 2004), since prevention is better than putting a 6-year-old on a diet (as some pediatricians do). Preschool educators (sometimes via guidelines for parents or requests to food providers) can also influence children’s nutritional intake, giving them time to eat and talk—and providing only nutritious food.