By the time children of overweight mothers reach 6 years of age, they are 15 times more likely to be obese, compared with children of lean mothers, results from a novel study suggest.
“These are kids at extraordinary risk for developing obesity,” the study's lead author, Robert Berkowitz, M.D., said in an interview. “These are not kids who are going to get thin later.”
The finding suggests that children of overweight mothers could become a target group for obesity prevention efforts, said Dr. Berkowitz, chair of adolescent psychiatry and executive director of the behavioral health center at the Children's Hospital of Philadelphia.
“Common sense prevention approaches [for children] include regular activity that's healthy and safe, cutting down on TV watching and computer game usage, and eating a healthy, low-fat diet with fruits and vegetables and portion control,” he told this newspaper.
“But we don't know that for sure because we haven't done the obesity prevention treatment at such a young age.”
For the study, which is the largest of its kind, he and his associates followed 33 children at high risk of obesity and 37 children at low risk of obesity based on the mother's prepregnancy body mass index (Am. J. Clin. Nutr. 2005;81:140–6). Mothers of high-risk children had a mean prepregnancy BMI of 30.3 kg/m2 while mothers of low-risk children had a mean BMI of 19.5 kg/m2. The study was confined to white children because they have different growth patterns compared with nonwhite children.
Investigators examined the children from 3 months of age to 6 years, including measurements of height, weight, skin fold thickness, and fat mass and lean mass by dual-energy x-ray absorptiometry (DXA).
They defined childhood overweight as a BMI at or above the 85th percentile for age and gender according to the National Center for Health Statistics/Centers for Disease Control and Prevention growth charts.
By age 2, no clinical differences were observed between the high- and low-risk groups, but by age 4 years, weight, BMI, lean body mass, and waist circumference were significantly greater among high-risk children, compared with their low-risk counterparts. Dr. Berkowitz said these factors translated into an 11-fold risk of obesity developing in high-risk children.
By age 6 years, the weight, BMI, lean body mass, and waist circumference had increased even more among high-risk children compared with their low-risk counterparts. Skin fold thickness also increased. In addition, for the first time, fat mass was greater in high-risk children compared with their low-risk counterparts (6.7 kg vs. 3.8 kg, respectively). So was percentage of body fat (24.7% vs. 18.8%, respectively). Dr. Berkowitz said these factors translated into a 15-fold risk of obesity developing in high-risk children.
Harsohena Kaur, M.D., a pediatrician at the University of Kansas, Kansas City, called the study “another piece of the puzzle” in gaining a better understanding of the epidemic of childhood obesity.
“We have been seeing bigger and bigger babies who are becoming bigger and bigger toddlers,” said Dr. Kaur, whose research interests include childhood obesity. “They seem to be bigger across the board. I have no idea how that's going to impact everything 20 years from now. This study is scary in that sense.”
Dr. Berkowitz said he was surprised there were no clinical differences between the high- and low-risk groups of children in the first 2 years of life.
“The kids at 1 and 2 years were identical in measures of height and weight and skin fold and body composition,” he said. “Maybe one of the things that's happening is that certain genes are beginning to turn on, or environmental influences are strong at this age.” A limitation of the study, he said, was its relatively small sample size. The National Institutes of Health supported the study.