Expecting Too Much from BMI
Flogging the limitations of Body Mass Index has become an easy sport. A new study in the International Journal of Obesity provides an excellent perspective on the problems with relying on BMI in isolation as an measure of health. Tomiyama and colleagues analyzed NHANES data for height, weight, and measures of cardiometabolic health, such as blood pressure, lipids, insulin resistance, and C-reactive protein, concluding:
Using BMI categories as the main indicator of health, an estimated 74,936,678 U.S. adults are misclassified as cardiometabolically unhealthy or cardiometabolically healthy. Policymakers should consider the unintended consequences of relying solely on BMI, and researchers should seek to improve diagnostic tools related to weight and cardiometabolic health.
You read that number right. Relying on BMI alone would misclassify the health of 75 million American Adults. That’s 30% of the population. That’s 75 million people whose employers have just been authorized to penalize or reward them, based on BMIs, through supposedly well-intended wellness programs.
In a companion editorial, Emily Dhurandhar, who chairs the Obesity Society’s Advocacy Committee, commented:
Policymakers should focus on strategies that truly improve the quality of life and health of people with obesity. These may include lifestyle interventions that incentivize physical activity, reduced energy intake, and encourage healthy habits, rather than a number on a scale. Due to the unintended consequences of BMI-based policies, there are many instances in which they may do more harm than good.
BMI can be a useful number, but it’s not an oracle. It’s just a signal that can cause much mischief when it’s used for setting goals, incentives, and penalties.
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February 10, 2016