Safety Community Environment Education Race Income Diet Neighborhood Poverty  You're a native-American baby born into the Oglala Sioux tribe, living on the Pine Ridge reservation in South Dakota. There are a lot of things that are going to make life a challenge for you, but one of the most perilous will be your weight. Chances are very good that your parents already have a weight problem; obesity is rampant in the 30,000-member community, and half the residents over the age of 40 have Type 2 diabetes. Their genes--and yours, of course--are part of the problem: researchers theorize that Native Americans have a higher than average tendency to gain and store weight, a protection in times of famines past but a risk factor in an America of caloric abundance.  Even without this so-called thrifty gene, you'd face an uphill battle to stay trim. Like many Americans in rural areas, the poorer Oglala Sioux have far less access to fresh fruits and vegetables than those in more connected settlements. This means you're likely to be filling up on high-calorie, processed foods, especially since fatty foods are cheaper than healthy ones, and your family--like more than half the families on the reservation--is probably poor. What's more, the calories you consume stick around, since you're not doing much to burn them off. Your school is probably too far away for you to reach it on foot. Playmates may be similarly distant. And don't even think about parks or playgrounds--multiple studies over the past several years have shown that low-income communities tend to have fewer recreational areas. Though it's all outside your control, nearly every aspect of your environment is pushing you toward gaining weight--which is why 43% of Native-American 5-year-olds in South Dakota are overweight or obese.  You're a Caucasian baby born in Boulder, Colo., and it's hard to count all your advantages in the good-health game. Chances are better than average that your parents are a healthy weight--only 11.9% of Boulder County residents are obese, compared with more than 30% for the U.S. as a whole. Colorado has the second lowest childhood overweight rate in the U.S., according to one survey. You live in a town blessed with parks and rugged natural beauty, where physical activity is all but mandatory and 14 triathlons were held last year--including one for kids as young as 3. But Boulder, with a population of more than 90,000 people, is large and dense; if you live in town, you can probably walk or bike to school. Chances are your family is at least middle class--the median income in Boulder County is significantly higher than the U.S. average. That means your parents can afford to shop at the many health-food stores in the city, where the organic chain Whole Foods moved its regional headquarters last year. Nearly every aspect of your environment is pushing you toward maintaining a healthy weight.  It's no secret that the U.S. has a crippling weight problem and that our children are hardly exempt. Rising obesity threatens to condemn a significant share of the next generation to a lifetime of weight-related disease, overburdening the already struggling U.S. health-care system. Though a recent study by Centers for Disease Control and Prevention (CDC) researchers found that childhood-obesity levels may finally have leveled off, more than 30% of American schoolchildren are still overweight, with little indication that rates will drop anytime soon. The CDC defines as overweight those children with a body mass index (BMI)--a rough factoring of height and weight--higher than the 85th percentile of figures from the 1960s and '70s, before the obesity epidemic hit. Obesity is defined as the 95th percentile. That's far from healthy. "The childhood obesity epidemic is a tsunami," says David Ludwig, an obesity researcher at Children's Hospital in Boston and the author of Ending the Food Fight. "We can see the wave heading toward shore."  This tsunami, however, is a highly selective one. It discriminates by race: according to the CDC's 2006 figures, 30.7% of white American kids are overweight or obese, compared with 34.9% of blacks and 38% of Mexican Americans. It discriminates by income: 22.4% of 10-to-17-year-olds living below the poverty line--less than $21,200 for a family of four--are overweight or obese, compared with 9.1% of kids whose families earn at least four times that amount.  It discriminates, perhaps most tellingly, by geography, with 16.5% of rural kids qualifying as obese, compared with 14.4% of urban kids, according to the 2003 National Survey of Children's Health. The poorest states of the South and Appalachia--Arkansas, West Virginia, Mississippi and Kentucky--have the heaviest children. Adult obesity levels triple when you cross north of 96th Street in Manhattan, leaving the mostly white and well-off Upper East Side for the predominantly minority, poorer neighborhood of Spanish Harlem. Even in trim Colorado, there are obesity hot zones.  All that provides a new way to look at--and attack--obesity. We tend not to talk about a problem like body weight in the language of infectious disease, but scientists do, knowing that like any other epidemic, the U.S.'s obesity scourge hits some communities harder than others. The skyrocketing increase in childhood obesity--the percentage of 6-to-11-year-olds classified as obese has nearly tripled since 1980--may argue strongly that the American environment has changed in a way that makes gaining weight much less avoidable. But the uneven distribution of the problem argues that who you are, where you are and how much your family has in the bank have a lot to do with whether your child will be claimed by the crisis or emerge unharmed.  "The environment makes it easier or harder for healthy choices to be the default choices," says Risa Lavizzo-Mourey, president of the Robert Wood Johnson Foundation, which last year pledged $500 million to end the rise in childhood obesity by 2015. "And adults create the environment that kids live in."  The geography of childhood obesity is largely the geography of poverty. There's no pretending that the problem--and resultant disparities in income, education and opportunity--will be easy to address, but there's no denying that it's imperative that we try. "It's the poorest and most deprived neighborhoods that suffer the most," says Adam Drewnowski, director of the nutritional-science program at the University of Washington. "This has to be fixed."
The rise in childhood obesity is a single problem with a whole lot of causes. Like any epidemic, it hits some groups hard and leaves others mostly alone. Which group your family belongs to depends on income, ethnicity, geography and more