As school cafeterias have started to replace white bread with whole wheat, serve only low-fat or nonfat milk, and set age-aligned calorie maximums, a new national study has found it’s not the school day that’s the problem. It’s summer.
Younger elementary school students gained weight faster over summer vacation than during the school year, according to the study published Wednesday in the journal Obesity. In fact, the percentage of overweight or obese students did not increase during the school year, it found.
These conclusions buck common assumptions about the summer break. It’s a time when children play outside, go for a swim, and ride their bikes around town, right? Perhaps because childrens’ summers are now filled with more screen time, less nutritious lunch and snack options, and irregular sleep, however, they are more at risk for weight gain, according to the researchers.
The study, which confirms a previous national study and other local studies, has led researchers to call for a shift in how the country and its schools tackle childhood obesity. Better meals, more physical education, and less sugary and salty snacks in vending machines under Michelle Obama’s Healthy Hunger-Free Kids Act (HHFKA) is the right idea, experts say. But schools should also teach students to make choices that they can take home with them, they add. They also recommend government policies such as a soda tax.
“The obesity problem does not originate in schools. Therefore, continued efforts to solve the problem through schools are likely to have disappointing results as many programs already have,” says Paul von Hippel, the lead author and an associate professor of public affairs at the University of Texas at Austin. “To implement school-based reform, we really have to think about the impact it will have on out-of-school based behavior.”
The study looked at a nationally representative sample of 18,170 kindergarten students. Starting in 2010, it followed changes in their Body Mass Index, or BMI – the relationship between their height and weight. The students were weighed once in the fall and once in the spring over a period that covered three school years and two summers.
Over that time, the prevalence of obesity increased from 8.9 percent to 11.5 percent, and the prevalence of overweight increased from 23.3 percent to 28.7 percent. But all of that increase occurred during the two summer vacations, not the school years.
The study acknowledges it’s not clear if students ate more in the summer. But it refers to previous research that has found children sleep less during the summer and watch more TV. It has also been shown children who live in hotter parts of the country are less active during the summer than children that live in cooler climates, the study adds.
The study did not find any differences in summer weight gain between children from lower or higher-income families, although a 2014 study by Harvard University found teenagers from lower-income families are more obese than wealthier teenagers because they exercise less and have less access to playgrounds, sidewalks, and other recreational facilities.
The study published Wednesday is the second national study of its kind. The first was a shorter, 2007 study, which von Hippel was involved in. The previous study found a similar trend among children who entered kindergarten in 1998. Other, more locally focused research has also confirmed these findings. Still, the latest study is surprising, says Michael Goran, founding director of the University of Southern California Childhood Obesity Research Center, and who was not involved in the study.
“The study shows that so far we haven’t really found an effective program that is school-based,” Dr. Goran tells The Christian Science Monitor in a phone interview on Thursday. “Even if we had a very strong, school-based programs, the fact of the matter is we have a very obesity-promoting environment outside of schools.”
Instead, Goran recommends programs and policies that seek to affect change off campus. He mentions taxing sodas and other sugar beverages or other ways to make sweet, salty, or fatty options more expensive, and vice versa.
Von Hippel of the University of Texas at Austin is also in favor of other creative attempts to tackle the problem. In addition to soda taxes, he mentions Chile’s efforts to promote more awareness about sweeter, fattier, and saltier foods. The country recently started to print warning labels on foods it deems unhealthy.
"We need to think about those kinds of steps if we’re actually going to make a dent in the problem," says von Hippel. Continuing to tinker with school lunches is not going to solve it alone, he says.