Clearly, it would be a mistake to conclude that obesity does not matter for our health or well-being, that it's without consequence to eat all the Krispy Kremes we want, throw out our sneakers and kick back and watch as our waistlines expand, says Dr. I-Min Lee, an associate professor of epidemiology and medicine at Harvard.

"Looking at dead versus not dead is not the only option,” she says.

Lee says the confusion about the impact of extra pounds on our health relates to how much weight conveys which risks.

A federal study published last fall in the Journal of the American Medical Association, for instance, concluded that obesity (BMI of 30 or higher) is associated with more than 112,000 excess deaths a year from heart disease in this country while both overweight (BMI of 25 to 29) and obesity together are associated with more than 61,000 excess deaths from diabetes and kidney disease. However, the study also found that being overweight but not obese was not associated with deaths from heart disease or cancer. In addition, extra weight seemed to actually protect against deaths from pneumonia, injuries and some infections.

When looking at all the many factors that can determine life expectancy for an entire population of millions of people, it can be difficult to tease out the role of a single factor, Lee says.

Additionally, with weight, things aren't always what they seem. Research that speaks to the benefits of exercise has suggested that it's possible to be "fit and fat" — that overweight, active people are healthier than their overweight, sedentary counterparts and possibly better off than some thinner, sedentary people. And smokers tend to be thinner than nonsmokers, but they aren't necessarily healthier, she notes.

Another federal study that looked at the growing longevity gap between the nation's rich and poor — a whopping 4.5 year difference (79.2 years versus 74.7 years) between people living in the least and most deprived areas of the nation — cited lifestyle and various other factors that can play a role in health disparities and longevity. Among them: lack of health insurance, limited access to health care, low-paying jobs, smoking, physical inactivity, unhealthy diets and neighborhoods that lack parks and good grocery stores selling fresh fruits and veggies.

Breaking things down even further, a study out earlier this week concluded that women living in some of the poorest counties in the country are lagging behind other women in life expectancy, primarily because of smoking, obesity and high blood pressure.

Family fitness
As for Sherrie Boughter and her family, they're not waiting for researchers to sort out all the possible risks of being overweight. They're banking on shaping up and slimming down to boost their odds of long, healthy lives.

She and her husband are both overweight and take blood-pressure medicine, so they're working alongside Justin to shed pounds. And they're hoping to get Justin's 2-year-old brother off on the right foot. "We're all doing it," she says.

Since starting the weight-loss program last September, Justin has lost 33 pounds. He meets with a trainer every other week and with a doctor every six to eight weeks. As part of his program, he exercises at a recreational center about five times a week and he's drastically cut calories.

Take after-school snacks, for instance. “He would have a sandwich and take the bag of Doritos to the couch,” says Boughter. Now Justin has a 100-calorie snack of an apple, banana or yogurt. "We don't buy Doritos anymore.”

Boughter says improving Justin's health to help him live as long as possible is a top priority, but there are other perks to his program that are evident right now.

"I don't get the feeling that people look at him as 'the fat kid' anymore," Boughter says. "He looks taller and he moves better and he’s more at ease with himself."

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