Efforts to prevent childhood obesity should begin in the womb and infancy to turn the tide on the startling increase in the number of overweight and obese children in this country, according to Dr. Matthew W. Gillman.
In a study of more than 120,000 children enrolled in a Massachusetts health maintenance organization, Dr. Gillman and his colleagues at Harvard Medical School in Boston showed that the prevalence of overweight and obesity among healthy, middle- class children younger than 6 years increased by 59% between 1980 and 2001. The increase in the number of overweight infants younger than 6 months during the same time period was 74% (Obesity 2006;14:1107–12).
Results of another study found that children who were overweight very young were not likely to outgrow that “baby fat” when they were older.
In fact, the definition of “overweight” is coming into question with the introduction of new growth standards by the World Health Organization (WHO), which differ fundamentally from the Centers for Disease Control and Prevention (CDC) standards and classify more American infants and young children as overweight. It is unclear whether the U. S. medical community will adopt or adapt these new growth charts.
Back to the Data
Children in the Harvard study were deemed overweight if their weight for body length/height was in the 95th percentile or higher. If that measure fell between the 85th and 95th percentile, children were considered at risk for overweight. With these cutoffs, 10% of the study population was overweight and 14% was at risk for overweight. For infants younger than 6 months, 6% were overweight and 11% were at risk for becoming overweight.
Although the Harvard study represented a regional population, the findings are consistent with those of two recent national nutritional surveillance systems—the National Health and Nutrition Examination Survey and the Pediatric Nutrition Surveillance System—that have documented significant increases in the prevalence of overweight children younger than 5 years old, Dr. Gillman noted.
The excessive weight trend does not stop in young children. In fact, that is where it starts. Children who are overweight as babies and preschoolers are at increased risk for being overweight or obese adolescents, according to data from another recent study that followed the growth and development of 1,000 U.S. infants over 10 years.
Using height and weight information collected at frequent intervals starting at age 2 years, Dr. Philip R. Nader of the University of California at San Diego and his colleagues showed that children who met the criteria for being overweight—defined as having a body mass index at or above the 85th percentile, compared with national statistics—at least once between the ages of 2 and 4.5 years—were five times more likely than their average weight peers to be overweight at age 12. And the risk of becoming an overweight adolescent increased by an order of magnitude relative to the number of times the child met the overweight criteria during the elementary school years (Pediatrics 2006;118:594–601).
The Health Consequences
The public health consequences of early excess weight gain are substantial. Epidemiologic studies over the past 15 years have demonstrated short- and long-term problems associated with overweight and obesity in childhood.
In the short term, overweight children are at risk for high blood pressure, respiratory problems, cardiovascular conditions, and early onset of type 2 diabetes. In the longer term, overweight children and adolescents are significantly more likely than their peers to become overweight adults, placing them at further risk for developing associated endocrine and cardiovascular comorbidities, as well as certain types of cancer, arthritis, and other serious problems later in life.
The rising rates of obesity and overweight in very young children that have set the stage for this unhealthy developmental cascade also have led to a shift in prevention efforts toward the identification of early factors that predict risk of subsequent obesity, which may allow for early targeted interventions.
Early Intervention
“Excessive weight at birth and excessive weight gain in the early weeks and months appear to be particularly harmful,” according to Dr. Gillman. And they also seem to be associated with certain prenatal factors. “Most evidence points to the fact that women are coming into pregnancy heavier than ever before and they are more likely to get gestational diabetes, which is a risk factor for child overweight. Also, women are gaining weight excessively during pregnancy, which is another risk factor,” he said in an interview.
Efforts to mitigate the risk of overweight in babies should include interventions targeted at parents that focus on avoiding excessive weight gain during pregnancy, preventing gestational diabetes, and promoting breast-feeding, which tends to be associated with leaner babies, according to Dr. Gillman.