Dr. Michael Fulks reviews recent guidance that challenges prevailing definitions of obesity and considers what this shift may imply for those who continue to rely on BMI as a primary measure.
A new consensus guideline for determining obesity was recently published by the Lancet Commission. It requires at least one other abnormal measurement (typically waist measurement or waist-ratio) in addition to elevated BMI unless BMI is >40. The guideline also allows a combination of at least two other measurements to define obesity when BMI is not elevated. The goal is to better identify those with excess body fat potentially impairing health or mobility missed by the BMI alone and to prevent identifying a subject as obese based only on BMI when excess fat is not present. Finding better tools than BMI to accurately identify those with excess fat associated with increased morbidity and mortality has been a struggle for both life insurers and clinicians for many decades. Up to now, no other measurement has been shown to be consistently better than BMI (703 x weight (lb.)/[height (in)]2). In addition to potentially improving diagnostic accuracy, these new Lancet guidelines introduce the concept of “clinical obesity” (organ dysfunction including hypertension and metabolic, or physical limitations) vs. “preclinical obesity” (no associated findings).
The guidelines were tested against 300,000+ participants of the “All of Us” (AoU) cohort (enrolled from 2018 to 2025, 53% White, median age 54) with results (and description of guidelines) reported in an article by Lindsay Fourman, et al. in JAMA Network Open. Using the new criteria rather than BMI alone, obesity increased from 43% to 69% of the cohort with the increase in obesity numbers being even higher at older age reflecting increased abdominal fat in this age group. Although some clinical diagnoses were more prevalent in the high-BMI plus one other measurement positive group, the increase in all-cause mortality, relative to those not obese, was similar between the high-BMI plus one and the OK-BMI but 2 other-measurements positive groups. Fortunately, only 0.2% of those classified as obese by BMI alone were reclassified as not obese by other measurements. A breakdown by age, sex, ethnicity and presence or absence of “clinical obesity” was included with interesting differences noted.
The good news for life underwriting departments is that incorrect classification of an applicant as obese based on BMI measurement alone is rare and continued use of BMI with individual exceptions as needed appears adequate. The bad news is that we are missing some higher risk applicants, especially at older ages where excess fat may be largely limited to abdominal obesity. The additional percentage of this multi-ethnic AoU cohort (and probably any life insurance applicant pool) identified as obese (and with increased mortality risk) based on these new criteria is a substantial concern. Unfortunately, identifying these individuals will still be problematic for insurers given the reduction in exams and limitations on acquiring accurate waist measurements or other testing results even if an exam is done. More favorable risk assessment may be appropriate for “preclinical obesity”. Further information on the increase in all-cause mortality for insurance applicants based on BMI can be found in this article.
About the Author
Michael Fulks, MD, Consulting Medical Director, is board-certified in internal and insurance medicine. After leaving practice, he served as a medical director, creating or editing several underwriting manuals and preferred programs. More recently, Mike has consulted for CRL participating in its mortality research on laboratory test results, BP and build, and in the development of risk-scoring tools for laboratory and non-laboratory data.