Understanding the Science Behind Childhood Obesity

04/13/2015 10:05 am ET | Updated Jun 13, 2015

Childhood obesity in America has reached epidemic proportions. We have long known about the troubling trifecta of insufficient exercise, processed food, and marketing that targets our most vulnerable consumers and their parents. In the last few months, however, new research has become available to help us see more clearly the evidence behind this growing crisis, and the public health solutions we need to design right away.

More than one third of U.S. children and adolescents were overweight or obese in 2012, according to the U.S. Centers for Disease Control and Prevention. In the past 30 years, obesity has more than doubled in children and quadrupled in adolescents. The consequences of childhood obesity, which include diabetes, heart disease, and other illnesses, are also rising. As this research indicates, overweight and obese young people have a very high probability of becoming obese adults, with all of obesity's heightened health risks.

This extraordinary prevalence constitutes a public health emergency more troubling than a new infectious disease: It puts at risk the health of those just getting started, a generation that will struggle against multiple chronic illnesses for their entire lives. Here at the Mailman School at Columbia University, our Obesity Prevention Initiative has been conducting vital research into childhood obesity. Several recent studies are especially illuminating.

Brand-new research conducted by Andrew G. Rundle, DrPH, an associate professor of epidemiology and a co-director of the Obesity Prevention Initiative, reveals that whether a child is normal weight, overweight, or obese at age 5 is hugely indicative of weight at age 50. If a child is obese at age 9, the correlation is even greater; at age 15, it's still worse. This extraordinary finding means that trajectories of weight gain starting at age 5 can be linked through ages 9 and 15 all the way to middle age.

In a series of additional studies, researchers have identified occurrences that take place during pregnancy that influence childhood obesity. For instance, about 50 percent of pregnant women nationally gain more weight during pregnancy than is recommended. That excess weight gain increases pregnancy complications and the likelihood that the child will be overweight. In a study published online last month in the journal Maternal & Child Nutrition, Dr. Rundle and others demonstrated that excessive pregnancy weight gain was associated with greater overall, and abdominal, body fat and obesity in children at age 7. Excessive weight gain during pregnancy was associated with an increased risk of childhood obesity of approximately 300 percent.

A separate study by Mailman School researchers published online in November in the International Journal of Obesity found that children who were exposed to antibiotics in the second or third trimester of pregnancy had a higher risk of childhood obesity at age 7. The research also showed that for mothers who delivered their babies by Caesarean section, whether elective or non-elective, there was a higher risk of obesity in their offspring.

In another study published in the American Journal of Epidemiology, researchers found that pregnant women in New York City exposed to air pollution in the form of higher concentrations of chemicals called polycyclic aromatic hydrocarbons, or PAHs, were more than twice as likely to have children who were obese by age 7 compared with women with lower levels of exposure. PAHs, a common urban pollutant, are released into the air from the burning of coal, diesel, oil and gas, or other organic substances such as tobacco.

Dr. Rundle notes:

Obesity is a complex disease with multiple risk factors. It isn't just the result of individual choices like diet and exercise. For many people who don't have the resources to buy healthy food or don't have the time to exercise, prenatal exposure to air pollution may tip the scales, making them even more susceptible to obesity.

These studies highlight the importance of efforts to reduce childhood obesity. Public health practitioners and healthcare providers should work with pregnant women to ensure proper weight gain and nutrition and to diminish risk of childhood obesity. To look more closely at these studies, you may wish to join "A Smart Start: Preventing Childhood Obesity," a symposium taking place on Thursday, April 16, at 1 p.m. at the Columbia University Medical Center, where a group of experts will explore these and related issues.

The federal government should make an ongoing priority of its Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), which provides grants to states for supplemental foods, healthcare referrals, and nutrition education for low-income pregnant women, new mothers, infants, and children up to age 5 who are found to be at nutritional risk. Schools should provide exercise classes and recreational activities for students. Communities should provide sidewalks, safe streets and parks to encourage walking and outdoor play, and they should ensure access to healthy foods. They should also take needed steps to reduce air pollution.

Combating childhood obesity is not just about personal decisions and behaviors, although everyone should strive to maintain appropriate body weight and fitness. Rather, it's about putting in place the public health systems that encourage proper nutrition and physical activity and provide the best possible environment in which pregnant mothers and children can thrive. Healthy choices should be easier to make. It's clear now that the implications of childhood obesity will be with us for decades to come.