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‘Normal-weight obesity’ linked to cardiometabolic risk in Chinese adults

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July 11, 2018

Normal-weight obesity — defined as a high body fat percentage in the setting of normal BMI — is relatively common in China, and the condition increases the risk for several cardiometabolic conditions, including diabetes and hypertension, according to findings published in Nutrition, Metabolism & Cardiovascular Diseases.

“Populations with [normal-weight obesity] are often neglected because they have no obvious changes in body shape,” Aihua Jia, of the department of endocrinology at Xijing Hospital in Xi’an, China, and colleagues wrote in the study background. “However, a number of studies have reported increased cardiovascular risks in [normal-weight obesity] populations, and [normal-weight obesity] may even increase the risk of death from cardiovascular disease in the elderly. Moreover, [normal-weight obesity] populations tend to develop some characteristic metabolic statuses such as low-grade proinflammatory state, increased oxidative stress, insulin resistance and lipid abnormalities, which can lead to increased risks of metabolic syndrome and cardiovascular disease-associated deaths.”

Jia and colleagues analyzed data from 23,748 Chinese adults aged at least 20 years with available body fat percentage measurements (assessed via biological impedance method) participating in the 2007-2008 China National Diabetes and Metabolic Disorders study (9,633 men). The researchers defined normal-weight obesity as excess body fat (at least 24% for men and at least 33% for women) in the setting of normal BMI, defined as between 18.5 kg/m2 and 23.9 kg/m2. Researchers classified patients as thin (BMI < 18.5 kg/m2); normal weight (BMI < 24 kg/m2); overweight (BMI < 28 kg/m2) and obese (BMI ≥ 28 kg/ m2). All participants underwent an oral glucose tolerance test, provided fasting blood samples for lipid profile measurements and answered questionnaires on personal and family history and unhealthy habits. Researchers used the Framingham risk score to predict the probability of CV events (sudden death or fatal/nonfatal myocardial infarction) within the next 10 years. Researchers used stepwise logistic regression analyses to assess the associations between normal-weight obesity and risk for diabetes, hypertension, metabolic syndrome and 10-year CV events.

Within the cohort, 1,771 participants (7.46%) were considered to have normal-weight obesity, 9,988 participants were normal weight (42.06%), 8,457 had overweight (35.61%) and 3,532 participants had obesity (14.87%).

Researchers observed that adults in the normal-weight obesity group had higher prevalence rates of Framingham risk score of 10% or higher, hypertension and metabolic syndrome vs. the normal-weight group. Moreover, gradual increases were observed in the prevalence rates of these conditions from the normal-weight obesity, overweight and obese groups.
Higher prevalence rates of diabetes, hyperlipidemia, hypertension and metabolic syndrome were seen in the normal-weight obesity group vs. the normal-weight group (P < .05 for all). Compared with the normal-weight group, the normal-weight obesity group had increased risk for diabetes (OR = 1.519; 95% CI, 1.262-1.828), a Framingham risk score of 10% or higher (OR = 1.973; 95% CI, 1.596-2.439), hypertension (OR = 1.525; 95% CI, 1.333-1.745) and metabolic syndrome (OR = 2.175; 95% CI, 1.92-2.463). The overweight and obese groups showed similar risks, according to researchers.

In subgroup analyses excluding participants with abnormal waist circumference, risk for cardiometabolic conditions persisted in adults with normal-obesity; however, when stratified by sex, risks persisted for women with normal-weight obesity in the prevalence rates for Framingham risk score of at least 10%, hypertension and metabolic syndrome, although not diabetes risk, according to the researchers.

 “This study shows a relatively high prevalence of [normal-weight obesity] among a Chinese population, especially in men,” the researchers wrote. “In addition, cardiometabolic risks significantly increase in a [normal-weight obesity] population, and such risks persist after excluding the effect of abdominal obesity. This study suggests that [normal-weight obesity], a subtype of obesity, may provide more information about the cardiometabolic risks compared with the more traditional obesity types based on BMI or [waist circumference].” – by Jennifer Byrne

Disclosures: The authors report no relevant financial disclosures.