Trends in Metabolic Phenotypes According to Body Mass Index Among US Adults, 1999-2018.

OBJECTIVE

To examine the prevalence, distribution, and temporal trends of metabolic phenotypes that are jointly determined by obesity and metabolic health status among US adults, overall and in key population subgroups.

PARTICIPANTS AND METHODS

A nationally representative sample of civilian, noninstitutionalized US adults aged 20 years and older from the National Health and Nutrition Examination Survey between 1999-2000 and 2017-2018 were included. Metabolic phenotypes were characterized jointly by body mass index and metabolic health: metabolically healthy underweight, normal weight, overweight, and obese (MH-OB); and metabolically unhealthy underweight, normal weight, overweight, and obese (MU-OB). Metabolic health was defined using the 2009 joint scientific statement for metabolic syndrome from the International Diabetes Federation Task Force on Epidemiology and Prevention, National Heart, Lung, and Blood Institute, American Heart Association, World Heart Federation, International Atherosclerosis Society, and International Association for the Study of Obesity as having 2 or less components (primary analysis) or no components (secondary analysis) of the following: waist circumference of 102 cm or greater in men and 88 cm or greater in women, fasting plasma glucose level of 100 mg/dL or greater, blood pressure of 130/85 mm Hg or greater, triglyceride level of 150 mg/dL or greater, and high-density lipoprotein cholesterol level of less than 40 mg/dL in men and less than 50 mg/dL in women.

RESULTS

Of 19,941 adults, the mean age was 46.9 years; 10,005 (50.6%) were female. From 1999 to 2018, the prevalence in primary analysis declined from 33.2% (465465 of 1646) to 25.1% (454454 of 2058) (difference, -8.09%; 95% CI, -12.5% to -3.70%) for metabolically healthy normal weight, whereas it increased from 9.92% (178178 of 1646) to 14.1% (277277 of 2058) (difference, 4.17%; 95% CI, 1.13% to 7.21%) for MH-OB (both P<.001 for trend). The prevalence of metabolically healthy underweight and overweight remained stable at about 1.62% (298298 of 19,94119,941) (95% CI, 1.38% to 1.89%; P=.34 for trend) and 22.2% (4,275 of 19,941) (95% CI, 21.4% to 23.0%; P=.14 for trend), respectively. The prevalence declined from 3.77% (72 of 1646) to 2.10% (68 of 2058) (difference, -1.67%; 95% CI, -3.22% to -0.12%; P=.006 for trend) for metabolically unhealthy normal weight, whereas it increased from 19.0% (343 of 1646) to 26.4% (574 of 2058) (difference, 7.41%; 95% CI, 2.67% to 12.2%; P<.001 for trend) for MU-OB. The prevalence of metabolically unhealthy underweight and overweight remained stable at 0.06% (11 of 19,941) (95% CI, 0.03% to 0.15%; P=.84 for trend) and 11.2% (2528 of 19,941) (95% CI, 10.6% to 11.8%; P=.29 for trend), respectively. Persistent differences in the prevalence of metabolic phenotypes were identified across multiple sociodemographic subgroups. For example, the prevalence of MH-OB increased from 7.58% (53 of 754) to 12.0% (79 of 694) (P<.001 for trend) for non-Hispanic Whites and 12.2% (60 of 567) to 18.4% (76 of 493) for Hispanics (P=.01 for trend) and remained stable at 22.6% (756 of 3,825) for non-Hispanic Blacks (P=.62 for trend and P=.05 for interaction). Results in secondary analyses revealed similar patterns.

CONCLUSION

From 1999 to 2018, US adults experienced major increases in the prevalence of both MH-OB and MU-OB, largely due to decreases in MH-N. The prevalence of MU-OB increased across all subgroups, with higher values observed in older adults and those with lower education and income levels.