Prevalence of Metabolically Healthy Obesity Increased From 1999 to 2018

Age-standardized prevalence of obesity, metabolically unhealthy obesity, and metabolically healthy obesity was found to be significantly increased among US adults from 1999 to 2018, according to findings of a study published in JAMA Network Open.

Researchers analyzed obesity data from 10 National Health and Nutrition Examination Survey (NHANES) cycles between 1999 to 2000 and 2017 to 2018.

Metabolically healthy obesity was defined as having a body mass index (BMI) of at least 30.0 without the presence of metabolic disorders of blood pressure, fasting plasma glucose, high-density lipoprotein cholesterol (HDL-C) levels, or triglyceride levels. Metabolically unhealthy obesity was defined as having a BMI of at least 30.0 with 1 or more of the metabolic disorders.

A total of 20,430 participants (50.8% women; mean age, 47.1 years; 68.8% non-Hispanic White) were included in the study.

Researchers noted that the proportion of metabolically healthy obesity significantly increased from 3.2% (95% CI, 2.6%-3.8%) between 1999 and 2002 to 6.6% (95% CI, 5.3%-7.9%) between 2015 and 2018 (P <.001). Specifically among patients with obesity at the beginning of the study, the rate of metabolically healthy obesity increased from 10.6% (95% CI, 8.8%-12.5%) between 1999 and 2002 to 15.0% (95% CI, 12.4%-17.6%) between 2015 and 2018 (P =.02).

Researchers observed significant decreases in the prevalence of elevated triglycerides (44.9% to 29.0%; P <.001) and low HDL levels (51.1% to 39.6%; P =.006). They observed significant increases in elevated fasting plasma glucose prevalence (49.7% to 58.0%; P <.001), but not high blood pressure levels (57.3% to 54.0%; P =.28).

Study limitations included that lack of a universally accepted definition of metabolically healthy obesity; because MHO is a transient condition, the number of patients with long-term MHO could not be completely and accurately assessed using a single measure of glycemic levels, blood pressure, and lipids; and the lack of generalizability of the findings in some subgroups.

Overall, the study authors noted that “the age-standardized prevalence of obesity, [metabolically unhealthy obesity], and [metabolically healthy obesity] increased significantly among US adults from 1999 to 2018.” They reported that this increase may be partly driven by the decrease in hyperlipidemia among patients with obesity because of increased awareness, diagnosis, and treatment of dyslipidemia.

Study authors concluded, “Although reasons for these trends may be complex and warrant further investigation, these results highlight the importance of reinforcing glucose management and reducing insulin resistance among adults with obesity.”