A new CDC study says that people with a body mass index in the overweight range have a lower risk of death, but BMI is an imperfect measure.

It’s survival of the heaviest, or is it?

In a bombshell editorial in last week’s New York Times, University of Colorado law professor Paul Campos claimed the medical community has created an artificial panic about obesity, stoking the public’s “absurd fear of fat.” Campos based his opinion on a recent analysis by Katherine Flegal of the Centers for Disease Control and Prevention (CDC), which concluded that people who are overweight or mildly obese have a five to six percent lower risk of death than their “normal” weighted peers.

When Flegal’s team crunched the numbers, they found that people with a BMI between 25 and 35—defined by the CDC as overweight or having grade 1 obesity—seem to be protected by their extra insulation.

Previous studies have also shown that patients with chronic diseases, such as diabetes or heart disease, and those who are elderly may benefit from a higher-than-normal BMI. It’s also possible that having a few pounds to spare comes in handy in the case of a sudden illness, such as pneumonia. The apparent contradiction between a high BMI score and a lower risk of death has been termed the “obesity paradox.”

Does this mean that being obese could save your life? Before we rush to Ben & Jerry’s for a bowl of Cherry Garcia, let’s take a closer look at BMI and what this measurement really means.

BMI is a simple formula used to estimate a person’s body fat content: weight in pounds, divided by height in inches squared, multiplied by 703. The CDC uses BMI, as opposed to more accurate measures of body fat such as skinfold thickness, to estimate obesity levels “because calculation requires only height and weight, [so] it is inexpensive and easy to use for clinicians and for the general public.”

The agency cautions that doctors should also take a patient’s diet, exercise level, family history, and risk factors for disease into account when determining his or her overall health and risk of death. Flegal’s study does not consider these factors.

“A better way would be to take more than one factor into account,” Dr. Eric B. Larson, Executive Director and Senior Investigator at the Group Health Research Institute and an expert in healthy aging and geriatrics, said. “In terms of the public’s health, activity levels and certain personal habits, like smoking, are probably the best predictors of mortality risk, other than genetics. If you can get these other measures you’ll probably get a more accurate picture of risk.”

Not only does BMI not offer a complete picture of a person’s health, other factors, such as being very muscular, can throw off the calculation itself. For example, according to the BMI formula, Minnesota Vikings center Joe Berger is “severely obese” at 6’5” and 305 pounds. As you age you also lose height, which changes your BMI score, even if you haven’t gained or lost a single pound.

Despite Flegal’s findings, there is still a large body of evidence about the dangers posed by obesity. Being overweight increases your risk of stroke, diabetes, and osteoarthritis, among other conditions.

“The take-away from all this is that when you look at being ‘overweight’ it’s not as bad as we thought, but if you’re fat, especially around the middle of your body, you’re at risk for a poor outcome,” Larson said. “Especially a lot of excess weight has serious metabolic effects and adds to insulin resistance, which likely plays a role in late life dementia risk. My fear is that if this obesity epidemic continues, the gains we’ve made in protecting elderly patients from dementia will be reduced.”

Thinner is not necessarily better, but there are many common-sense ways to keep yourself in good health and to lower your risk of death from a chronic disease (not including trips to Micky D’s).

“I think people get discouraged when they look at their BMIs and say, ‘Hey look, I’m overweight,’” Larson said. “It’s easier to develop healthy habits than it is to lose weight. I say to my patients, ‘If you can do walking, three times a week at minimum, but ideally everyday, it will really help.’”