Obesity isn’t good for you -- it can lead to myriad health problems and can shorten life -- but not always. Recent research reported in the Journal of the American Medical Association (Sui, et al. 2007;298:2507-2516) indicates that even obese older people, if they also are physically fit, have a reduced risk of death compared to similarly fat but less fit folks.
The researchers assessed the cardiovascular fitness of 2,600 adults (aged sixty or older, about 80% males) by treadmill exercise tests, calculated their body mass index (BMI), and measured their percent body fat and waist circumference (as a measure of body fat distribution). The participants were then followed for twelve years, on average, and their health status and longevity (and causes of death) were monitored.
Those individuals who died during the study were more likely to have been smokers and to have had cardiovascular disease, high blood pressure, and lower HDL ("good") cholesterol at the onset of the study than did survivors. Survivors were also significantly more fit and slightly younger than those who died.
In general, a very high BMI, over 35, was associated with a 29% increased mortality risk, while people in the highest fitness group (measured as their ability to do treadmill exercise) had an astonishing 75% reduced risk of death -- the more fit the person, the lower the risk of death.
When the effects of excess adiposity (obesity) were examined, the researchers found that individuals with abdominal obesity (that is, an "apple" rather than a "pear" shape) had a 25% higher risk of mortality than those without that body fat distribution. But if the data were statistically adjusted to include the effects of fitness, this effect did not persist; thus the more fit, the less the central adiposity seemed to matter. Indeed, the authors noted that fit participants had lower death rates than unfit people within each level of adiposity ranging from a normal BMI of 18.5-24.9, up to overweight BMI of 25-29.9.
The take-home message of this research is that a high level of physical fitness seems to be protective against the mortality-accelerating effects of obesity -- especially for men over sixty years of age. As the researchers noted, "moderate and higher fitness levels favorably influence mortality risk across categories of body composition." In other words, keep moving!
See also: ACSH's survey of Nutrition Accuracy in Popular Magazines.