It’s hard to go more than a day without hearing about America’s obesity epidemic. Nearly 40% of the country is plagued by this problem, and the correlation with heart problems, cardiovascular disease, and diabetes renders this a scary prospect for the future of the country. But what if extra body fat isn’t the problem? What if there was simple solution to the problem? According to Dr. Steven Blair, a former professor of Exercise Science at the University of South Carolina, there is.
Back in 1999, Blair and colleagues conducted an observational study of nearly 22,000 men to see if there was a relationship between fitness, body composition, and mortality. Subjects were divided into three categories: lean, overweight, and obese. Within these three categories, subjects were either deemed fit or unfit depending on their aerobic endurance. At the end of the observation period, the fit men were determined to be at a significantly lower risk for all-cause mortality and cardiovascular disease mortality than their unfit counterparts, regardless of body fat composition.
A similar study was conducted in 2002, but this time the research focused on female subjects. The results were the same -- low cardiovascular fitness was a better predictor of mortality than body mass index (BMI). By 2007, Blair and colleagues had replicated the results in a longitudinal study observing both men and women, with an average follow-up time of 12 years.
However, Blair’s claims that fitness is far more important than body fat percentage has not gone uncontested. Work by Dr. Frank Hu at the Harvard School for Public Health did show that regular physical activity was beneficial at all adiposity levels, but any advantages were not significant enough to offset the risks of obesity. Unlike Dr. Blair, Dr. Hu and colleagues view low levels of exercise and high BMIs as independent and equal predictors of mortality.
Furthermore, a 2017 study found that obese individuals were at a significantly higher risk for coronary heart disease when compared to normal weight individuals. This phenomenon was magnified for those who had metabolic conditions such as diabetes, hypertension, and hyperlipidemia, all of which have been associated with obesity.
These studies have come from the careful analysis of millions of patients over a several year period. It’s hard to argue with numbers and trends as strong as these, but there are certain limitations to these studies that must be addressed. Perhaps most importantly for this conversation, the determination of whether an individual is considered normal weight, overweight, or obese is usually derived from BMI calculations. This formula is based on the height and weight of a person, and does not take physical activity into account. To account for this, many studies measure a participant’s physical activity via self-reporting mechanisms -- a precariously subjective approach.
According to Dr. Blair, this is exactly what makes his research so profound. In an interview with The Guardian, Blair explained the treadmill test his team used to force individuals to 90% of their maximal endurance efforts. In his view, this “proves” the athletic conditioning of survey participants, regardless of what they claim their status to be. “You simply can’t tell by looking whether someone is fit or not,” Blair explains. “ But when we look at these mortality rates in fat people who are fit, we see that the harmful effect of fat just disappears.”
Disclaimer: I am not a licensed nutritionist nor a registered dietician. The opinions expressed in this article are my own, and each individual is ultimately responsible for his/her dietary and nutrition practices. Please consult a physician before starting a new dietary program.