Although obese adults have had improvements in their blood pressure and cholesterol levels during the past three decades, their hemoglobin A1c (HbA1c) levels have increased, according to a survey analysis.
The rising HbA1c levels may lead to a higher incidence of type 2 diabetes and cardiovascular complications.
Lead researcher Fangjian Guo, MD, PhD, of the University of Texas Medical Branch, and colleagues published their results online in the Journal of the American Heart Association on July 13.
They examined 18,626 obese adults who participated in the National Health and Nutrition Examination Survey (NHANES) from 1988 through 2014. The adults were at least 20 years old and had a body mass index (BMI) of 30 kg/m2 or higher.
The researchers found that the mean BMI significantly increased from 34.7 kg/m2 in 1988-1992 to 36 kg/m2 in 2011-2014. During that same time period, the mean waist circumference significantly increased from 43.3 in. to 45.2 in. (110.1 cm to 114.8 cm).
Further, the mean systolic blood pressure significantly decreased from 126.1 mm Hg in 1988–1992 to 124.4 mm Hg in 2011–2014, while the mean HbA1c level significantly increased from 5.7 percent to 5.9 percent. Further, the mean blood total cholesterol significantly decreased from 214.5 mg/dL to 193.7 mg/dL.
During the study, the prevalence of obese adults with diabetes, elevated cholesterol and blood pressure increased 37 percent, from 16.4 percent in 1988-1992 to 22.4 percent from 2011-2014. The increase was found in all ages, sexes and racial/ethnic subgroups.
In addition, the prevalence of participants free from all three cardiovascular disease risk factors remained stable at approximately 15 percent of obese adults.
The researchers cited a few limitations of the study, including a small sample size that may have hindered extensive subgroup analyses of each age, sex and racial or ethnic group. They also did not assess physical activity during the study because they found that it significantly increased from 2007-08 onward.
However, they mentioned that the NHANES contained nationally representative data that allowed them to assess cardiovascular risk factors and overall cardiovascular health status among obese adults.
“Although some data point to a leveling off of prevalence rates of obesity in recent years, our data indicate that overall metabolic health is declining among people with obesity in the United States,” the researchers wrote. “Furthermore, deteriorating metabolic health can be attributed primarily to worsening glycemic health because mean values of HbA1c have been increasing, whereas mean blood pressure and lipid metrics have been improving. These patterns of worsening metabolic health constitute an increase in risk of type 2 diabetes mellitus and underlie increasing prevalence rates for diabetes mellitus.”