A Boy, a Girl and a Scale

Obesity risk factors among children vary according to their sex

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Ask 20 people why children are more overweight these days, and you're likely to get 20 answers. And it's possible all of them — or none of them — are correct.

It's difficult to pick out all the possible factors that might contribute to obesity among children. One recent study looked specifically for differences between girls and boys and found several.

Boys were less likely to be obese if they played sports, but girls were not. Girls were less likely to be obese if they drank more milk, but not so for boys.

But all the children were more likely to be obese if they watched a lot of TV or ate school lunches.

"Ask your pediatrician about a nutritious diet for children."

This study, led by Morgen Govindan, BA, of the Michigan Cardiovascular Research and Reporting Program at the University of Michigan, looked for risk factors for obesity that may differ between girls and boys.

The researchers gathered data from 1,714 sixth graders, including their height, weight, blood sugar, lipids, blood pressure and resting and recovery heart rates.

The researchers compared this data and the children's body mass index (BMI), taking into account their sex.

BMI is a ratio of a person's height to weight, and is used to determine if a person is a healthy weight. Children at the 95th percentile or higher for weight for their age and sex were considered obese.

Unsurprisingly, the children who were not obese had healthier measurements in their physical assessment, such as blood pressure, lipid levels and blood sugar.

The researchers identified two behaviors that the obese children were more likely to engage in, regardless of whether they were boys and girls.

Children who regularly ate school lunches were about 1.3 times more likely to be obese than children who did not regularly eat school lunches.

The researchers were not able to look at the specifics of the school lunches for the children, but they noted "...previous research suggests the nutritional value of lunches being consumed in schools is not optimal, consisting of nutrient-poor, calorie-rich foods."

In addition, children who watched at least two hours of TV a day were about 1.2 times more likely to be obese than children who watched less TV.

Additional "screen time" (TV, movies, video games, computers, etc.) has been shown to be linked to obesity in many past studies.

Among boys, the researchers found that those who were involved in school sports teams or vigorous physical activity were slightly less likely to be obese (about 10 percent less likely).

Greater physical activity was defined as at least 20 minutes of "vigorous" physical activity or 30 minutes of "moderate" physical activity at least five times a week.

There was no difference in obesity risk among girls in terms of their participation in school sports or their physical activity levels.

Meanwhile, girls were slightly less likely to be obese (about 19 percent less likely) if they drank at least two servings of milk daily.

The milk connection did not show up for boys, and it's not clear why it exists for girls. One possibility is that the girls are drinking milk instead of sugary drinks like soft drinks or juice.

The researchers noted that knowing the various possible risk factors for obesity among school-age children may help in targeting interventions to reduce their risk of obesity.

Deborah Gordon, MD, a dailyRx expert who specializes in nutrition, said the higher cholesterol  and triglycerides levels seen in the obese children was not surprising.

"I'm disheartened to read that eating school lunches is positively correlated with obesity," Dr. Gordon said. "Shouldn't lunchtime be a part of the school day, and healthy lunches be the norm in schools rather than the exception?"

But she noted that this study's findings match up with some others that have found milk to be protective against obesity.

"Not surprising, but also disheartening, is the association with obesity seen in both genders for those watching two or more hours of television daily," she said.

"The takeaway messages from the study are that all children will benefit from healthier school lunches with greater nutrient density and less starchy, sugary and empty calories," Dr. Gordon said.

"Equally true is that strategies to increase a preference for physical activity over television might prove very helpful," she said. "Further strategies with particular attention to gender differences might be determined with studies designed to further investigate questions raised by this study."

This study was published August 12 in the journal Pediatrics. The authors declared no conflicts of interest.

The research was funded by University of Michigan Health System, the Thompson Foundation, the Hewlett Foundation, the Mardigian Foundation, the Memorial Healthcare Foundation, the William Beaumont Health System Foundation, the Robert C. Atkins Foundation, the Ann Arbor Area Community Foundation, the Allen Foundation, AstraZeneca Healthcare Foundation, Borders Inc. and the Robert Beard Foundation.

Review Date: 
August 13, 2013
Last Updated:
August 22, 2013