It's no secret that Americans are getting fatter. Nearly two thirds of U.S. adults, an estimated 127 million, are overweight. According to the Centers for Disease Control and Prevention, about 39 million were heavy enough to classify as obese in 2000 (the most recent data available), representing a 60 percent jump in less than a decade.

Older Americans aren't the only ones struggling with their weight. Almost one third of American kids are considered overweight, and nearly one in six is obese, putting children at a higher risk for health problems more commonly seen in adults, such as hypertension, asthma and diabetes. In their new book, "Generation Extra Large: Rescuing our Children From the Epidemic of Obesity" (Basic Books), Lisa Tartamella and coauthors Elaine Herscher and Chris Woolston (senior editor and contributing editor at Consumer Health Interactive, respectively) explore the rise in child obesity, noting changes in the culture and at home that make it harder for kids to keep off the extra pounds. NEWSWEEK's Jennifer Barrett Ozols spoke with Tartamella, a nutritionist at Yale-New Haven Hospital's Centers of Nutrition, about the causes of child obesity and potential solutions. Excerpts:

NEWSWEEK: The percentage of kids who are overweight has quadrupled since the 1970s. How did we get to this point?

Lisa Tartamella: It's basically starting in the playpen. It's not one specific reason, but a combination of factors. Kids are surrounded by high-calorie foods, and they don't have as many opportunities to run and burn off those calories. Two culprits in particular stood out as we did our research: soda consumption and TV viewing. We know kids are drinking more soda. Is it the only factor? No. But it is a contributing factor. The average teenage boy drinks 19 ounces of soda a day. Meanwhile, TV keeps kids stuck on the couch and gives them the opportunity to be exposed to endless advertisements for fast food and junk food, and it gives them an opportunity to snack. You don't burn many calories clicking a remote control.

Also, families where both parents are working now outnumber those with just one working. And it is difficult for working parents to even feed themselves--let alone their kids--or to exercise. We're pressed for time so we get pizza or takeout. Right now, Americans get about one third of their calories from food prepared away from home each day--that's a meal a day. And they tend to be higher in fat and calories and lower in fruits and vegetables and dairy.

What about the food kids get at school?

So many school districts are in poor financial shape and are trying to cover expenses any way they can. So when big soda companies dangle multimillion-dollar contracts, can you blame them for signing? Can you blame the schools for bringing fast food into cafeterias to cut costs? In the meantime, schools are also cutting back on physical education and--in some cases--recess. But there are some schools that are taking a stand--whether it's by only allowing soda to be sold after school or looking at innovative ways to raise funds without relying on soda or candy sales.

How big a role does poverty play?

A lower-income neighborhood may not be as safe for kids to go out and play, so it's hard to blame parents for wanting their kids to stay inside with the TV versus playing in an unsafe area. And residents in lower-income neighborhoods might not have accessibility to more nutritious food options like fresh fruits and vegetables. But high-calorie foods aren't necessarily expensive. A dollar goes a long way at fast-food restaurants.

How serious is child obesity from a health perspective?

I'd say we are looking at a generation that may have a shorter life expectancy than their own parents. We have pediatricians diagnosing kids with type 2 diabetes. That used to be adult-onset diabetes, but now it is appearing in younger children. They also have high blood pressure and high cholesterol levels.

Are obese children suffering from metabolism problems or is it really just the result of eating too much and not getting enough exercise?

Obesity is a complex issue. There are factors you can't control like genetic links, but there are also controllable ones like exercise and food choices. You can't pick your parents, but you can pick what you eat and how often you exercise.

In other words, children whose families have a history of obesity are not doomed to be obese themselves?

Yes, that's where the parents and the importance of creating a healthy household come in.

What about weight-loss surgery for teenagers and adolescents?

We don't address it in the book, but my feeling is that it is not a cure-all. It is still a tool used for weight loss, but it is not a simple solution. It still involves making a commitment to permanently changing eating habits and exercising more. There are also emotional aspects tied in with obesity. There are issues that got them to being overweight initially, whether they're chronic dieters and have an all-or-nothing attitude about food or their eating is stress induced. The emotional aspects of eating don't necessarily go away. So the mental health aspect can't be forgotten. When you're evaluating whether someone should have surgery, it is important to look at the whole picture.

Are there times when diet and exercise aren't enough?

My philosophy has always been about changing lifestyles. But when you're talking about morbid obesity and the success rate of a typical diet is losing 10 percent of your weight, that may not be enough.

What role do parents have in controlling their children's weight?

Parents serve as role models and can have more influence over their child's weight than just about anyone else. We don't want to point blame. It's not the parents' fault. But it's their responsibility to create a healthy home environment. You can't get far if you don't have the support of the people who make your meals, buy the groceries and set the rules. Parents are a major part of their children's environment. The kids that have had the most success [in losing weight] were those who had the most committed parents. When parents are committed to creating a healthy home environment, the kids can lose weight and keep it off.

What role should the government play--if any?

We need a national policy to better regulate what food and drinks we sell in schools. And government education mandates should be funded. If schools can't afford pencils and notebooks, how can they offer PE classes to the kids who need them most? The government needs to stop nurturing relationships with the food industry and start nurturing kids instead.

Why hasn't this become a national health-policy issue?

I think it's because it's been chalked up to being a personal responsibility issue. But think of it this way: one in six kids are seriously overweight. If you had the same number of kids in school with the flu, you'd have public health specialists and epidemiologists flooding the community to determine the root of the problem and to deal with it. We know obesity exists in such staggering proportions and yet we don't look at it in the same way. Why don't people look at obesity as a disease? As we wrote in the book, it's likely to overtake tobacco as the leading cause of preventable death this year.

Do you see the situation getting better--or worse--in the near future, and why?

I think we have done a really good job of raising awareness. The statistics have been flashed in front of everyone's faces long enough. But what have we done about it? The numbers are still getting worse. We have well-documented the epidemic, but it will only get worse unless we start committing to making changes on all levels--in the home, in schools. Our book is really a rally cry to make some changes before it gets worse.