The ongoing debate about whether one can be obese and yet healthy is not new, but it in recent years it has gained momentum and recent studies aimed at providing convincing evidence have produced inconsistent results, which prompted Anika Zembic, MPH, of the German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthertal, Germany and colleagues to seek an evidence-based definition.
They started out with these standard considerations:
- Metabolic health, they wrote, is characterized by the presence of two or fewer of these criteria: “waist circumference, 102 cm (men) or greater than 88 cm (women); BP greater than or equal to 130/85 mm Hg or using BP-lowering medication; triglyceride level greater than or equal to 150 mg/dL or using lipid-lowering medication; high-density lipoprotein cholesterol level less than 40 mg/dL (men) or less than 50 mg/dL (women); and fasting glucose level greater than or equal to 110 mg/dL or prevalent diabetes.”
- Cardiovascular health is characterized by blood pressure less that 130/85 mm Hg without the use of BP-lowering medications, fasting glucose less than 100 mg/dL, hemoglobin A1C less than 5.7% in the absence of glucose-lowering medications, triglycerides less than 150 mg/dL, total cholesterol less than 240 mg/dL, HDL less than 40 mg/dL in men or less than 50 mg/dL in women or if they are not using lipid-lowering medications.
And they boiled them down to this definition for metabolically healthy obesity (MHO):
- Systolic BP less than 130 mm Hg and no use of BP-lowering medication.
- Waist-to-hip-ratio (WHR) less than 0.95 for women and less than 1.03 for men.
- No prevalent diabetes.
And, when they matched those criteria to samples drawn from two population-based cohorts—the third National Health and Nutrition Examination Survey (NHANES-III) and the UK Biobank—they found that, “Regardless of body mass index, all metabolically unhealthy groups displayed increased risks,” they wrote in JAMA Network Open.
“Of all significant continuous factors, the combination of systolic BP and waist-to-hip ratio showed the highest area under the receiver operating characteristic (CVD mortality: 0.775; 95% CI, 0.770-0.781; total mortality: 0.696; 95% CI, 0.694-0.699). Thus, MH was defined as systolic BP less than 130 mm Hg, no BP-lowering medication, waist-to-hip ratio less than 0.95 for women and less than 1.03 for men, and no self-reported (i.e., prevalent) diabetes. In both cohorts, metabolically healthy obesity was not associated with CVD and total mortality compared with metabolically healthy normal weight,” they added.
They analyzed NHANES-III and UK Biobank data to identify individuals age 18 to 75, with no history of cardiovascular disease and a body mass index (BMI) of at least 18.5. Individuals were required to fast at least six hours before examination. Zembic and colleagues studied data from 12,341 NHANES-III participants and 41,431 UK Biobank participants.
BMI groups were normal weight (18.5-24.5), overweight (25.0-29.9) and obese (≥30). In addition to race, age, and ethnicity data, the authors collected blood pressure and anthropometic measurements as well as serum levels of triglycerides, total cholesterol, high-density lipoprotein cholesterol, glucose, and hemoglobin A1c levels. From NHANES-III participants they also collected “C-reactive protein, insulin, γ-glutamyltransferase, and alanine aminotransferase levels.”
In an invited commentary published with the Zembic paper, Ayana K. April-Sanders, PhD, and Carlos J. Rodriguez, MD, MPH, both of Albert Einstein College of Medicine in Bronx, New York, wrote that the “new definition places an emphasis on the WHR and does not account for dyslipidemia. Although easy to measure, BMI is considered an insufficient measure of body fat content because it fails to account for muscle mass and bone density and does not reflect fat distribution. Waist circumference is commonly used to capture abdominal obesity in prior MHO definitions; however, WHR is a more effective measurement of central adiposity, with WHR having the strongest gradient with incident CVD because not all excess weight is the same and will differ in its association with health risks… The present study also suggests that, although still relevant to metabolic syndrome risk, the effect of dyslipidemia on CVD death and mortality risk may be weaker among individuals with obesity.”
In what will strike many as good, if surprising news, the “MHO phenotype was also prevalent with more than 40% of individuals with obesity in the NHANES-III cohort meeting the criteria. In addition, individuals with MHO as identified in this study were healthier, more educated, and less likely to have low income than those of the metabolically unhealthy groups, regardless of BMI category,” April-Sanders and Rodriguez wrote.
In addition to bypassing lipid profiles completely, the definition offered by these authors also differs from previous definitions that placed an emphasis solely on waist circumference. Waist circumference does provide an estimate of visceral fat but also includes subcutaneous abdominal fat, which is considered lest dangerous. “In contrast, hip circumference is a proxy of lower body fat, which might have protective effects on metabolism. In support of stronger predictive power of WHR compared with waist circumference, WHR was more associated with mortality than waist circumference in individuals with high BMI.”
Zembic et al claimed their study is the first to systematically assess “cardiometabolic risk factors for a possible definition for the MHO phenotype,” but it is not without limitations, including the lack of data on changes in both body weight and metabolic factors.
“Furthermore, body fat distribution might differ according to race/ethnicity and our proposed WHR cutoff might not be suitable for all populations, especially Asian populations, which were underrepresented in both cohorts,” they added.
The authors concluded that they have developed a new definition that should be used in both clinical and research settings.
“Our results suggest that people with MHO classified by this definition are not at increased risk for CVD or total mortality. Metabolically unhealthy individuals have a substantially higher risk, which is not explained by conventional definitions of MH. Thus, our new definition may be important not only to stratify risk of mortality in people with obesity, but also in people with overweight and normal weight,” they wrote.
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A new definition of metabolic health identified in this study may allow clinicians to stratify risk of mortality not only in people with obesity but also in people with overweight and normal weight.
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Be aware that this study suggests that obese individuals who do not have prevalent diabetes, maintain systolic BP less than 130 mmHg without use of BP-lowering medications, and who have a WHR less than 0.95 for women and less than 1.03 for men are metabolically healthy and do not have an increased risk of cardiovascular events.
Peggy Peck, Editor-in-Chief, BreakingMED™
Zembic reported grants from German Federal Ministry of Education and Research (BMBF) DZD grant 82DZD00302 during the conduct of the study.
Rodriguez reported receiving grants from the National Institutes of Health and Amgen outside the submitted work.
Cat ID: 187
Topic ID: 76,187,730,305,308,914,187,307,795,518,917
