Two new studies look at how to classify obesity
One study assessed a new obesity framework that includes clinical comorbidities, while another analyzed the impact of including waist circumference in risk assessment.
Two new studies looked at classification of obesity and its associated health risks.
The first study showed that one in five overweight adults could be reclassified as having obesity rather than overweight according to the European Association for the Study of Obesity's (EASO) new framework, although their mortality risk was similar to that of adults with normal weight. The study was published July 8 by Annals of Internal Medicine.
The EASO's framework incorporates measures beyond body mass index (BMI), adding clinical comorbidities. To validate it, researchers studied data from 44,030 U.S. adults ages 18 to 79 years who participated in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2018.
The researchers found that with the new definition of obesity, 18.8% of the study population who were previously identified as having overweight based on BMI alone could be newly classified as having obesity. The most prevalent comorbid conditions among persons newly identified as having obesity were hypertension (79.9%), arthritis (33.2%), diabetes (15.6%), and cardiovascular disease (10.5%). Similar mortality risk was found among the newly identified persons with obesity and adults with normal weight and the same medical conditions, whereas persons with a BMI of 30 kg/m2 or greater had almost a 20% higher hazard of dying. However, when compared with persons with normal weight who did not have major comorbidities, newly identified persons with obesity had 50% higher hazard of dying. Higher risk was seen among persons with obesity compared with persons with overweight according to both the new EASO framework and the traditional BMI definition. The researchers said more studies are needed to examine whether persons newly identified as having obesity by the EASO framework would benefit from obesity treatment.
The second study was a prospective cohort study finding that BMI-specific waist circumference thresholds modestly improved mortality risk stratification in postmenopausal women, with larger waist circumference predicting greater mortality in women across BMI groups. The findings support recent International Atherosclerosis Society and International Chair on Cardiometabolic Risk recommendations to include waist circumference measurement with BMI in patient screenings to identify high-risk obesity phenotypes. The study and an accompanying patient summary were published July 8 by Annals of Internal Medicine.
Researchers analyzed data for 139,213 postmenopausal women ages 50 to 79 years from the Women's Health Initiative and divided them into a development cohort (67,774 participants), validation cohort 1 (48,335 participants with a high prevalence of overweight or obesity), and validation cohort 2 (23,104 participants from diverse, geographically separate centers). Predicted risk was determined based on a mortality model, the mortality model plus BMI (BMI model), and the mortality model plus BMI plus BMI-specific waist circumference thresholds (BMI-WC model). BMI categories included normal weight, overweight, and obesity classes 1 to 3, and waist circumference thresholds were 80, 90, 105, and 115 cm.
Nearly all women with class 2 or 3 obesity had waist circumferences of 88 cm or larger. After stratification, the researchers found that mortality risk was greater for women in the same BMI categories with larger waist circumference than their counterparts with normal waist circumference. Overall, stratifying BMI categories by waist circumference thresholds modestly improved risk stratification for all-cause mortality in healthy postmenopausal women with a high prevalence of overweight or obesity.
These results suggest that clinical guidelines for assessing adiposity would benefit from the incorporation of waist circumference with BMI measures, the authors said.
An editorial accompanying both studies stated, “With the expansion of effective obesity treatment options, it's time we match our advances in therapeutics with improvements in diagnosis and risk assessment. The [two studies] offer new insights but also highlight the challenges of this task.”