As the childhood obesity epidemic continues to boom, new research suggests genetics and poor eating habits may not be the only causes. A study released Tuesday from Boston Children's Hospital found women who gain excessive weight during pregnancy are more likely to have overweight and obese children.
David Ludwig, director of the hospital's New Balance Foundation Obesity Prevention Center, studied the relationship between a woman's weight gain during pregnancy and her children's body mass index at age 12. Ludwig analyzed BMI data on more than 90,000 children in Arkansas, where height and weight measurements are required each year in public schools, and found that the children whose mothers gained more weight during pregnancy had higher BMI scores.
"What we found was that pregnancy weight gain indeed strongly predicted childhood body weight and obesity," Ludwig says.
To rule out the influence of genetics and home environments, Ludwig analyzed data only on children who had siblings. Until this point, Ludwig says, it was unknown if the link between a mother's weight gain during pregnancy and her child's weight later in life was caused by shared genes because previous studies have relied on comparing unrelated mother-child pairs.
"On average, siblings are going to have the same proportion of genes that lead to obesity versus leanness and on average they will have the same home environment," Ludwig says.
When comparing the women who gained the least amount of weight during pregnancy to those who gained the most weight, the difference in their children's BMI scores was half a unit, which Ludwig says can range from two to three pounds.
Although a weight difference of a few pounds might not seem like a significant difference, Ludwig says it could make a "significant" contribution to the obesity epidemic for two reasons: children who are overweight or obese early in life are more likely to remain obese into adulthood, and the link between pregnancy weight gain and obesity could be passed on through generations.
"We're looking at potentially long-lasting effects," Ludwig says. "What happens for the mother during just nine months could have effects throughout childhood and perhaps throughout life for the next generation."
Additionally, Ludwig estimates that the link could explain hundreds of thousands of new cases of childhood obesity each year throughout the world.
In the past three decades, obesity has more than tripled in adolescents, according to the Centers for Disease Control and Prevention. In 2010, more than one-third of children in the United States were overweight or obese. The CDC warns of the impact of obesity, which can include immediate effects such as high blood pressure, sleep apnea and social and psychological problems, as well as long term effects including a higher risk of heart disease, stroke and several types of cancer.
"We know that obesity can affect virtually every organ system in a child's body," Ludwig says. "The study suggests that the best time to begin childhood obesity prevention efforts may be before birth."