You may have heard that childhood obesity rates are finally starting to drop a teensy bit after years of climbing ever higher. This is fantastic news for a nation that now counts 17% of its residents under the age of 20 as obese.
True, the declines have been seen only in certain areas of the country such as New York City, Philadelphia, California, and Mississippi.
And the drops are small (in New York City between 2007 and 2011, a 5.5% decline in the number of obese schoolchildren) and largely confined to higher-income, white kids who are less likely to be obese than poor, black children.
But the numbers do seem to be real. The one thing that researchers don't know is exactly why the declines are happening.
No doubt, aggressive anti-obesity programs are the big reason, with some of the most encouraging trends seen in cities that have instituted comprehensive initiatives to fight the scourge.
Philadelphia, in many ways the poster city for this type of program and the only area which has recorded improvements across different ethnic and racial groups, has made major changes in school-food environments, including eliminating sugary drinks in vending machines, replacing whole milk with skim milk and removing deep fryers from cafeteria kitchens.
Corner stores in Philly are also in on the action with hundreds now offering fresh fruits and vegetables, low-fat dairy products, lean meats, and whole grains. Some have even taken on new shelving and refrigeration so as to be able to sell more healthy items.
New York City recently banned sales of sugary drinks in containers larger than 16 ounces and now requires chain restaurants to disclose calorie counts on menus.
"What they successfully did in New York and Philadelphia was tie together very comprehensive programs with public-policy efforts and all the other efforts going on in the community," says Bob Siegel, MD, medical director of the Center for Better Health and Nutrition at Cincinnati Children's Hospital. "They touched all the bases and they marketed it very well and had the education to go along with it."
But are there other factors that are also helping to lower obesity rates?
For instance, efforts to curb out-of-control salt consumption may be paying off too. While more salt has not directly been linked with obesity (nor do we know for sure that salt consumption is down), research has shown that children who eat a lot of salty food also drink a lot of sugary beverages, a well-known contributor to obesity.
Also, "foods that have high salt content are often high in calories," says Tracie Miller, MD, professor of pediatrics at the University of Miami Miller School of Medicine. So cutting down on salt also curbs calories.
Over the last decade, there's also been a 14% drop in antibiotic prescriptions for children and adolescents aged 17 and younger.
Again, a direct link between antibiotics and obesity hasn't yet been drawn, but one hypothesis is that the drugs might play a part in the obesity epidemic. One early study found that mice given antibiotics accumulated more body fat than mice who weren't. Another study found that children who received antibiotics in the first six months of life were more likely than other kids to be heavier later on.
Interestingly, points out Ashis V. Barad, MD, chief of pediatric gastroenterology at Scott & White Hospital in Round Rock, Texas, the first six months of life is critical for "growing or creating the bacterial flora of your gut garden." These billions and billions of organisms have an effect on food absorption and digestion.
Bisphenol A (BPA), a common chemical found in some hard plastics, linings of food cans, and other food packaging has also been linked to childhood obesity. Perhaps efforts to reduce the amount of BPA we're exposed to are also paying off? In recent years, manufacturers have eliminated BPA from many products intended for children, like baby bottles. However, it's seems unlikely that a chemical eliminated from baby products in 2008 or 2009 could have such an impact.
One big factor, at least in Philadelphia, may be the effort to provide better sidewalks, playgrounds, bike trails, and after-school activities, which promote physical activity, says Dr. Miller.
As part of its anti-obesity program, the City of Brotherly Love has created almost 10 miles of conventional bike lines, 9 miles of bike "sharrows" (markings indicating where bikes can safely navigate within traffic) and 1,800 bicycle racks.
All of this is in keeping with Michelle Obama's Let's Move program to increase physical activity (and improve nutrition) in children.
Of course, no one knows if these successes will be replicated elsewhere, or even if they'll continue in these selected areas.
"This is very encouraging but I don't take this message as 'We've done it,'" says Dr. Miller. "We need to keep pushing and not stop because it's easy to go back."
"It's extraordinarily complex how the [obesity] problem developed. It's multifactorial and involves just about every element of life," adds Dr. Siegel. "It took a lot of time to put these terrible things together with the environment and it's just taken a lot of time to piece things together that work."