The study, published in the New England Journal of Medicine, examined 7,738 children from a "nationally representative sample," according to The New York Times. Researchers measured the children's weight and height every year for seven years, from 1998 to 2007. The study found that 12.4% of the participants were obese when they started kindergarten — obesity being defined here as having a BMI at or above the 95th percentile. By eighth grade, 20.8% were considered obese, and half of the obese kindergarteners were still obese. The study suggests, then, that the heavier kindergarteners were four-to-five times more likely to become obese than their thinner classmates.
Ruth Loos, a professor of preventative medicine at the Icahn School of Medicine at Mount Sinai in New York, told the Times that the study's main message is that "obesity is established very early in life, and that it basically tracks through adolescence to adulthood." The official conclusion states "Incident obesity between the ages of five and 14 years was more likely to have occurred at younger ages, primarily among children who had entered kindergarten overweight." While some of the overweight kindergarteners lost the excess weight by the time they got to eighth grade, and some of the normal weight students got heavier, it seems that every year, a child is less likely to move out of his/her weight range.
The researchers in this study can't explain why childhood weight is so indicative of a person's future weight, though genetics can't be ignored in this equation. The authors of the study say that it could be a combination of a genetic predisposition to obesity and an environment in which parents encourage overeating. Researchers didn't measure the children's weights before kindergarten, but they did know all the students' birth weights. And, they found that children who became obese were at least 8.8 pounds at birth. So, if a child is heavier at birth, are they then set up for BMI disaster? Dr. Stephen O'Rahilly, an obesity researcher and professor at the University of Cambridge, says genetics play a huge part. He told the Times, "We have known for 50 years that BMI is highly heritable. Surprise, surprise, if you tend to be fat, you tend to be fat at an early age."
The takeaway from the study is that school efforts to rectify childhood obesity are distributed like blanket statements. Thin children have different needs than overweight children. And, to suggest a healthy living plan for all children does a great disservice to those who are more in need.
It's also important to note that the study took place during the years 1998 to 2007, when kids were still being elected class president by promising soda machines in the cafeteria. Real changes to school meals, emphasis on physical activity, and a focus on nutrition are fairly recent additions to curriculum. While this study is the first to evaluate a full range of childhood weight, we'd like to see a subsequent study that evaluates the effectiveness of new school programs geared at weight loss and healthy living. (The New York Times)