Background: The prevalence of obesity has more than doubled in the USA in the past 30 years. Obesity is a significant risk factor for diabetes, cardiovascular disease, and other clinically significant co-morbidities. This paper estimates the medical care cost savings that can be achieved from a given amount of weight loss by people with different starting values of body mass index (BMI), for those with and without diabetes. This information is an important input into analyses of the cost effectiveness of obesity treatments and prevention programs.
Methods: Two-part models of instrumental variables were estimated using data from the Medical Expenditure Panel Survey (MEPS) for 2000–2010. Models were estimated for all adults as well as separately for those with and without diabetes. We calculated the causal impact of changes in BMI on medical care expenditures, cost savings for specific changes in BMI (5, 10, 15, and 20 %) from starting BMI levels ranging from 30 to 45 kg/m2, as well as the total excess medical care expenditures caused by obesity.
This study was an attempt to use MEPS data to see how much losing weight might save people in health care costs, both with and without diabetes. The topline results showed that, on average, obesity raised health care costs by just more than $3500 per person. That means that obesity cost the US more than $315 billion a year.
But the paper goes further, and it’s important to dig down. The costs are NOT equally spread over obese individuals. People with class 1 obesity, or those whose BMI is greater than 30 but less than 35, pretty much have no elevated health care costs. When we say lots of people in the US are obese or overweight, many of them still have BMIs less than 35.
The paper further reports that a person who has a starting BMI of 40, and can lose 5% of their weight, might expect to see reductions in health care costs of $2137. But only about 6% of adults have a BMI that high. Losing 5% of weight if you have a starting BMI of 35 would save you $528. Losing that weight if you’re starting with a BMI of 30 would save you $69.
The savings also depend on whether you have diabetes. For instance, the savings that might be achieved by a 5% weight loss for a person who has BMI of 40 is $2123 if they have type 2 diabetes, but only $643 if they don’t.
My point is this: Talking about the “costs of obesity” in the aggregate makes it sound like if everyone in the US would just lose a little weight, we’d save massive money. But it’s not that simple. The vast majority of the costs of obesity are located in a relatively small group of people, those who are extremely obese and have diabetes.
If our goal is to reduce the cost to the US for obesity, we should likely focus on that small group of people, who are also likely the hardest to reach and influence. Trying to get lots of people who have a BMI of 30-35 to lose some weight might make them feel better, but won’t influence health care spending in the US much at all.