‘Metabolically healthy obesity’ on the rise, but still rare

The proportion of Americans with “metabolically healthy obesity” has risen alongside the general rise in obesity over the past two decades, but “healthy” numbers remain low, new data shows.

Figures from the National Health and Nutrition Survey (NHANES) indicate that “metabolically healthy obesity” – defined as obesity without any associated metabolic disorder, such as high blood pressure or increased blood sugar – has more than doubled in the overall population from 1999 to 2018, but still remained a small proportion of the overall growing population suffering from obesity.

Additionally, the increase in “metabolically healthy” obesity has occurred primarily among people aged 60 and over, men and white adults, as well as those with higher incomes, private insurance or class 1 obesity.

And over the study period, the overall prevalence of obesity increased from 28.6% to 40.9% of the population, along with the corresponding increase in “metabolically unhealthy” obesity.

“We observed a low prevalence of [metabolically healthy obesity] and a significant and growing burden of [metabolically unhealthy obesity]…These results highlight the need for effective strategies to … prevent obesity-related complications in obese people, especially among vulnerable subpopulations,” says Jiang-Shui Wang, MBBS, University of Science and technologies from Huazhong, Wuhan, China, and colleagues. , who published their findings on March 9, 2023 in JAMA network open.

Asked to comment, former Obesity Society President Steven B. Heymsfield, MD, said Medscape, “Metabolically healthy obesity is kind of a warning light – you’re overweight and very lucky. … It’s not just a law of nature that the minute you’re overweight or obese, all those bad things happen. You bring obesity onto your genetic make-up, and that can vary greatly from person to person. … You can also have metabolic syndrome and absolutely normal weight.

Is “metabolically healthy obesity” a useful concept?

Heymsfield explained that the concept of “metabolically healthy obesity” is of limited use since a person’s risk factor profile can change over time.

“You base a definition of health on how a person looks at the time and the different risk factors. … Obesity is a disease with a long gestation period. It remains subclinical for many years .. When people get older, you start to see things manifest clinically that you didn’t see when they were 20 or 30…not in everyone, but in a lot of people.”

Additionally, he noted, many people may have a high body mass index (BMI) due to large bone structure and/or large muscle mass, with relatively low fat mass. “It’s not that rare in the BMI range around 30 kg/m², especially among youth. At a BMI of 30, the body fat range is very wide.”

For this reason, he advises clinicians to measure not only waist circumference, which is recommended but not often done in the clinic, but also hip circumference to determine waist-hip ratio (WHR).

This measurement is supported by the World Health Organization (WHO) as a more accurate assessment of obesity than BMI as well as a better predictor of cardiovascular risk (WHR ≥ 0.90 cm in men and ≥ 0.85 cm in women identifies a significant metabolic risk, according to WHO), said Heymsfield, Pennington Biomedical Research Center, Baton Rouge, Louisiana.

Thus in the case of a person with a BMI of 30 kg/m² and a normal waist circumference or waist-to-hip ratio with no other metabolic risk factors, “this person is probably not obese or overly fat. They are probably muscular. It may not be totally clear on the surface,” a- he observed.

Metabolically healthy obesity is increasing, but prevalence remains low

The NHANES is a series of nationally representative U.S. surveys conducted in 2-year cycles, and researchers looked at data from 1999 to 2000 and 2017 to 2018.

“Metabolically healthy obesity” was defined as a BMI of 30 kg/m² or more without metabolic disturbances, such as high blood pressure, increased fasting blood glucose, or changes in lipids, based on established thresholds.

Included were 20,430 adult participants, of whom 7,386 were obese. For the entire study population, the prevalence of age-standardized obesity increased significantly, from 28.6% in 1999-2002 to 40.9% in 2015-2018 (P for trend < .001).

At the same time, the age-standardized prevalence of metabolically healthy obesity approximately doubled, from 3.2% to 6.6% (P < .001).

And among obese people only, the increase in the prevalence of metabolically healthy people increased from 25.4% to 34.3% (P < .001).

“Our results suggest that the overall increase in metabolically healthy obesity was primarily due to the decrease in dyslipidemia in obese adults,” possibly due to increased awareness and treatment, say Wang and colleagues. colleagues.

Elevated blood pressure remained stable and elevated fasting blood sugar increased, with the researchers stressing that “priority should be given to strengthening glucose management and reducing insulin resistance in obese people.”

The study was supported by grants from the National Natural Science Foundation of China, basic research funds for central universities, and Shanghai Municipal Science and Technology Major Projects. The authors report no other relevant financial relationships. Heymsfield sits on the advisory board of Novo Nordisk, owns shares in Merck and receives research funding from Pfizer and Versanis.

JAMA network open. Published online March 9, 2023. Full Text.

Miriam E. Tucker is a freelance journalist based in the Washington, DC area. She is a regular contributor to Medscape, with other work published in The Washington Post, NPR’s Shots blog, and Diabetes Forecast magazine. She’s on Twitter @MiriamETucker.

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