They also looked at the teens' physical activity levels. "If you're sleeping less, you're fatigued during the day and less likely to be active," Mitchell says. "But the link we observed was not fully explained by lower levels of physical activity." Another possibility is that being awake longer means more opportunities to eat, but Mitchell's team did not look at dietary intake. Past research has also found that sleep deprivation might alter the body's regulation of hormones leptin and ghrelin, which control satiety and hunger. Or, the problem may not the total caloric intake but the timing of eating, Mitchell says. He noted mice studies where the nocturnal critters became obese if they ate during day and night but remained a normal weight if they only ate at night.
Regardless of the mechanism, these findings also support the notion that the entirety of kids' 21st-century environment—not their self-control or reduced physical activity—is the key culprit in the rise in obesity. "People like to make obesity a disease of blame, but the last 40 years has not seen an epidemic of our children losing willpower," Freedhoff says. "There are dozens and dozens of these environmental factors. Unless we reengineer our children's environments, we are not likely to see any changes in children's weights."
Freedhoff points to cities such as Philadelphia and New York, where modifying children's environments, especially in schools, may be responsible for recent reductions in obesity. Philadelphia removed sugary drinks from vending machines in 2004, then reduced snack food serving sizes, removed deep fryers from school cafeterias and replaced whole milk options with 1 percent and skim. Outside of school, more than 600 corner stores participate in the Food Trust initiative to stock their shelves with healthier snacks. New York has instituted new nutrition standards in schools (pdf) and daycare centers, as well as screen-time limits in day cares. The two metropolises also have some of the most comprehensive menu labeling laws in the country.
"This is a lot more complicated than ‘eat less, exercise more,'" Freedhoff says. "If weight management or childhood obesity prevention and treatment were intuitive, we'd have a lot of skinny kids running around." Freedhoff himself is developing a program for families that focuses on "redrafting" kids' and families' environments, starting with more home cooking. "Every parent would die for their child, but most won't cook for their children on a consistent basis with whole ingredients," he says.
But Freedhoff also says the problem of increasing childhood obesity cannot be tackled by parents alone. He suggests starting with changes within school boards, sports teams, PTAs and others who already care about kids. "What I'm amazed by is the constant use of fast food to pacify children and reward children—there is no event too small for candy or fast food." There are many places communities could start: making school lunches healthier, ditching vending machines and access to fast food inside schools, not celebrating sports wins at fast food joints, and ending the use of candy or fast food as rewards, such as "pizza days" and other unhealthy food-themed school events, to name a few. "People don't appreciate that parents are around children a minority of their days," he says, so it really will take a village to turn back the clock in terms of kids' environments. "If we had a time machine, it would be the world's best weight-loss program," Freedhoff says. "It's the world that has changed, not people."