On January 28, 2014, President Barack Obama said in the State of the Union speech,” As usual, our First Lady sets a good example. Michelle’s Let’s Move partnership with schools, businesses, and local leaders has helped bring down childhood obesity rates for the first time in thirty years – an achievement that will improve lives and reduce health care costs for decades to come. “ Really? We’ve already reviewed Michelle Obama’s premature “Mission Accomplished”. Perhaps the President and First Lady should take note of recent research which indicate the childhood obesity crisis is far from over.
Just two days after the State of the Union, the New England Journal of Medicine published a study by Cunningham and colleagues, “Incidence of Childhood Obesity in the United States.” Much attention has been paid to the prevalence of obesity, meaning the total number of persons with the condition in the population. Incidence, on the other hand, is the number of new cases appearing in the population at a given time. So Cunningham et al, looked at a database of 7,738 children who were in kindergarten in 1998 and were measured 7 times between 1998 and 2007.
They found that, on entering kindergarten (age 5.6 years) 12.4% were obese and another 14.9% were overweight. In eighth grade (age 14.1 years) 20.8% were obese and 17% were overweight. The incidence dropped between fifth and eighth grade. Overweight 5-year-olds were four times as likely as normal weight children to become obese. Among children who became obese between 5 and 14, nearly half had been overweight and 75% were above the 70th percentile. Hispanic and non-Hispanic black children had higher rates of obesity than white children. Children from the wealthiest 20% of families had the lower prevalence of obesity in kindergarten than those in all other socioeconomic groups and this difference increased through the eighth grade.
Overweight kindergartners had 4 times the risk of becoming obese by age 14 as normal weight kindergartners. Overweight children from the two highest socioeconomic groups had five times the risk of becoming obese as normal-weight children of similar socioeconomic status.
The incidence of obesity between the ages of 5 and 14 years was 4 times as high among children who had been overweight at age of 5 as among children who had a normal weight at that age. The researchers’ findings are significant in addressing public policies regarding obesity. “First,” they state, “a component of the course to obesity is already established by age of 5 years…Second, obesity incidence among overweight children tended to occur early in elementary school. “ The study supports closer examination of the roles of the early-life home and pre-school environments, intrauterine factors and genetic predisposition.
(Although not discussed in the paper, age 5-6 is regarded as the time of a child’s lowest Body Mass Index (BMI) and the beginning of “adiposity rebound” – a period of increasing weight into adulthood. This is a normal phenomenon all children go through.)
New studies show how babies might be already programmed for excessive weight gain. One study, by Jane Wardle and colleagues, show that greater appetite (either due to higher food responsiveness or lower satiety responsiveness predicted rapid growth up to 15 months of age among twins. The second study by the same group showed that low satiety responsiveness is one of the mechanisms by which genetic predisposition leads to weight gain in an environment rich with food.