Maintaining a Healthy Weight Could Mitigate Excess Spending Linked to Both Low, High BMI

Medical expenditures were higher among individuals with a body mass index (BMI) outside the “healthy weight” range, reflecting the broader health burden associated with both low and high BMI, according to a research letter published today in JAMA Network Open.¹

Evidence Gaps Persist in Understanding the Economic Burden of BMI

The researchers noted that maintaining a healthy BMI, defined as 18.5 to 24.9, is associated with a lower risk of chronic disease and reduced medical expenditures.² Despite this, only 26% of US adults had a healthy BMI between 2015 and 2018.¹ They highlighted that estimates of BMI-associated medical costs have not been updated since 2016 and that few studies have examined the association between being underweight and medical expenditures.

To address these gaps, the researchers conducted a study providing updated estimates of BMI-associated medical expenditures among privately insured US adults in 2022. They linked IQVIA’s PharMetrics Plus claims data with ambulatory electronic medical records to identify eligible adults aged 18 to 64 years with at least 1 BMI measurement and 11 or more months of continuous insurance enrollment in 2022.

After adjusting for age, sex, US Census region, and confounding conditions, the researchers used fractional polynomial regression to estimate associations between continuous BMI and medical expenditures. Using healthy weight as the reference group, they also applied generalized linear models to assess differences by BMI category, with additional analyses stratified by sex, age, and care setting.

Both Low, High BMIs Linked to Elevated Medical Spending

The study population included 704,864 individuals, 55% of whom were female (n = 393,235), with a median (IQR) age of 49 (37-57) years. Most patients (44.6%; n = 314,157) were classified as obese, followed by overweight (30.9%; n = 217,762), healthy weight (23.5%; n = 165,587), and underweight (1%; n = 7358).

Among the adults with obesity, 3.7% (n = 26,405) had a BMI greater than 45, indicating class 3 obesity, which is associated with a substantially elevated risk of severe health conditions.³

The researchers estimated total medical expenditures to be $8009 for individuals at a healthy weight. In comparison, expenditures were $1776 higher for those with obesity, $1242 higher for patients considered underweight, and $317 higher for participants classified as overweight.¹

Specifically, expenditures were 16% higher among individuals considered underweight (expenditure ratio, 1.16; 95% CI, 1.11-1.20) and 22% higher among those with obesity (expenditure ratio, 1.22; 95% CI, 1.21-1.23). The researchers also noted that excess expenditures were not uniform within the obesity category, reaching $3388 among individuals with a BMI of 45 or higher.

Age-stratified analyses showed that older adults experienced greater absolute BMI-related expenditures. Compared with individuals at a healthy weight, excess costs were $1843 (35%) higher among those aged 18 to 24 years with a BMI of 45 or higher (expenditure ratio, 1.35; 95% CI, 1.22-1.49) and $4146 (42%) higher among those aged 55 to 64 years with a BMI of 45 or higher (expenditure ratio, 1.42; 95% CI, 1.36-1.49).

Additionally, sex-based analyses indicated that overweight- and obesity-associated excess expenditures were greater among female adults ($3604) than male adults ($2995) with a BMI greater than 45.

By care setting, inpatient care accounted for the highest excess expenditures overall. Meanwhile, outpatient care represented the largest source of excess spending among individuals who were overweight or obese, reaching $1353 at BMIs of 45 or higher.

Achieving or Maintaining a Healthy Weight Could Reduce Future Medical Spending

The researchers acknowledged several limitations, including that the study population reflected health care–seeking adults rather than the general population; this may partially explain why obesity-related excess cost estimates were lower than those reported in national survey-based studies. In addition, the underreporting of certain conditions, such as eating disorders, may have biased underweight-related expenditure estimates. Nonetheless, the researchers expressed confidence in the relevance of their findings for informing future interventions.

“Supporting individuals in achieving or maintaining a healthy weight through accessible, evidence-based strategies could reduce long-term BMI-associated risks and expenditures,” the authors concluded.

References

1. Wang S, Kompaniyets L, Belay B, Lange Pierce S, Goodman AB. Medical expenditures by body mass index among privately insured US adults aged 18 to 64 years, 2022. JAMA Netw Open. 2026;9(1):e2555436. doi:10.1001/jamanetworkopen.2025.55436
2. Cawley J, Biener A, Meyerhoefer C, et al. Direct medical costs of obesity in the United States and the most populous states. J Manag Care Spec Pharm. 2021;27(3):354-366. doi:10.18553/jmcp.2021.20410
3. Class III obesity (formerly known as morbid obesity). Updated February 19, 2025. Accessed January 26, 2026. https://my.clevelandclinic.org/health/diseases/21989-class-iii-obesity-formerly-known-as-morbid-obesity