Recognizing and preventing childhood obesity. Part 1 of 2

Childhood obesity is one of the most challenging problems facing pediatricians today. Approximately 10% of children younger than 2 years old and 21% of children between 2 and 5 years of age are overweight.¹ However, there are disparities in the prevalence of childhood obesity. For example, non-Hispanic black and Hispanic preschool-aged children have a higher prevalence of obesity than non-Hispanic white children; in older children, socioeconomic disparities also exist.^2,3 Young children with excess weight have an increased risk for obesity in the future.⁴ Unfortunately, few effective treatments exist for children who already are overweight. Therefore, prevention of obesity is paramount.

How early should prevention begin? Experts have suggested that gestation to early infancy is a critical period in which physiologic changes occur that greatly influence a child's later risk for obesity.⁵ Will recognizing the early signs and red flags associated with the development of obesity lead to a change in the growth trajectory and long-term health of the next generation?

Normal growth patterns in infants and toddlers

On September 10, 2010, the CDC released a recommendation that all US medical providers use the World Health Organization (WHO) growth curves for children aged 0 to 24 months.^8,9 The reasons for this recommendation are compelling. Although the CDC growth curves are a growth reference, describing how a particular group of children grew at a certain time, the WHO curves represent a growth standard, describing how healthy children grow in optimal conditions.⁸ In the CDC sample, the rates of breastfeeding initiation, exclusivity, and duration are variable but overall very low.¹⁰

For example, in NHANES III (1988-1994), which is a component of the CDC growth curves, 45% of children were never breastfed, and only 21% of children were breastfed for at least 4 months.¹¹ In contrast, WHO growth standards use a sample of infants who were breastfed for 12 months and predominantly breastfed for at least 4 months. Since growth patterns differ between breastfed and formula-fed infants, the WHO growth curves show a faster weight gain in the first few months of life than the CDC growth curves; by about 3 months, this pattern reverses. In addition, the new CDC recommendations suggest the 2nd and 98th percentiles on the growth charts as the cutoffs for concerns of unhealthy growth.⁸

As clinicians begin to use the WHO charts, they will see that fewer young children will be classified as underweight. Likely, clinicians will note that a slowed weight gain between 3 and 18 months among breastfed infants is normal, and they will be more likely to reassure parents that supplementation or a switch to formula feeding is unnecessary. In addition, it is anticipated that clinicians will more easily identify formula-fed infants who are gaining weight too rapidly, because these children will more likely be crossing growth percentiles in an upward direction. Pediatricians will then have an opportunity to counsel parents of these infants at an age at which the amount and type of infant feeding can be modified.