Led by Feifei Wang, Ph.D., of the University of Michigan, the researchers used a database of nearly 36,000 auto workers and their spouses to analyze the relationship between body weight and health care costs. Using height and weight data, the researchers calculated each subject's body mass index (BMI), a standard measure of the relative percentages of fat and muscle mass. (The formula for calculating BMI is the person's weight in kilograms divided by the height in meters squared.)
Starting at a BMI of 25—the lower end of the "overweight" range—health costs rose steadily along with BMI. Adjusted for age and sex, annual medical costs increased by about $120 (four percent) for each one-point increase in BMI. Drug costs increased by $83 (seven percent) per one-point increase.
Costs continued to rise for subjects within the "obese" category—BMI of 30 or higher. For a person with a BMI of 35, medical costs were nearly $600 higher and drug costs $413 higher than for a person with a BMI of 30.
Higher BMIs were linked to increased health costs in 11 of 18 disease categories, with the greatest impact on costs for musculoskeletal and circulatory diseases. For each one-point increase in BMI, costs related to diabetes increased by about $6 and costs for heart disease increased by $20. For each step up in BMI, the likelihood of diabetes medical claims increased by twelve percent and claims for heart disease increased by five percent.
Previous studies have shown that health costs rise along with BMI. However, these prior studies have tended to overlook the fact that health costs also increase for people who are underweight—BMI of 17 or less. The new study was designed to provide more accurate estimates of the rate of cost increase at BMIs above the normal weight range—BMI of 18 to 24.9.
Dollar estimates of the increase in health costs per unit of BMI are likely to vary across industries and insurance types. However, the researchers believe their results provide a simple way to quantify the costs associated with obesity. For employers, the data will give an idea of the savings possible through weight loss in overweight or obese workers, or the costs associated with weight gain.
Dr. Wang and colleagues call for "more strategic and effective ways" of addressing continued increases in obesity and associated health costs. "Creative approaches are needed to reach a higher percentage of the obese population and modify their behavior in the long run."
ACOEM, an international society of more than 5,000 occupational physicians and other health care professionals, provides leadership to promote optimal health and safety of workers, workplaces, and environments.