The study, led by Feifei Wang, Ph.D., of the University of Michigan, calculated the body mass index (BMI) of nearly 36,000 autoworkers and their spouses to analyze the relationship between body weight and health care costs. For those who started 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 (4 percent) for each 1-point increase in BMI. Drug costs increased by $83 (7 percent) per 1-pound 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 were $413 higher than for a person with a BMI of 30.
Higher BMIs were linked to increased health care costs in 11 of 18 disease categories, with the greatest impact on costs for musculoskeletal and circulatory diseases. For each 1-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 12 percent and claims for heart disease increased by 5 percent.
Study Focused on Above-Normal Weight Range
Previous studies have shown that health costs rise along with BMI. However, these prior studies have tended to overlook the fact that health care costs also increase for people who are underweight (BMI of 17 or less), according to University of Michigan research team.
The University of Michigan 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, the researchers point out. However, they believe their results provide a simple way to quantify the costs associated with obesity.
'Creative Approaches' Needed
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, according to the University of Michigan research team.
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," she said.