Obesity continues to trend up among women over the past decade

Four in 10 women in the United States are obese, 1 in 10 women has a body mass index above 40 kg/m², and significantly more women are obese than a decade ago, according to a large study published June 7 in JAMA.

In contrast, obesity rates among men in the United States have remained stable since 2005, said Dr. Katherine Flegal of the National Center for Health Statistics. “Other studies are needed to determine the reasons for these trends,” she and her associates wrote.

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Between 1980 and 2000, obesity rates in the United States rose significantly among both men and women. Between 2000 and 2004, rates rose significantly for men, but not women. Rates then leveled off for both sexes through 2012. To further explore these trends, Dr. Flegal and her associates calculated the prevalence of obesity (BMI greater than 30 kg/m²) and class 3 obesity (BMI greater than 40 kg/m²) for 2,638 men and 2,817 women aged 20 and up during 2013-2014, the most recently available 2-year data period from the National Health and Nutrition Examination Survey (NHANES). The researchers also examined trends in obesity since 2005, based on NHANES data from 21,013 adults (JAMA. 2016 Jun 7. doi: 10.1001/jama.2016.6458).

About 38% of adults in the United States were obese during 2013-2014 (95% confidence interval, 36%-40%), including about 40% of women and 35% of men, the researchers found. A total of 7.7% of adults had a BMI of at least 40, including 5.5 % of men and 9.9% of women.

During the decade from 2005 through 2014, the prevalence of obesity among women rose significantly from 35.6% to 41.1% (P = .004), even after the investigators adjusted for age, race and Hispanic origin, smoking status, and education. Among men, the adjusted prevalence of obesity remained about 35% during this time period. Likewise, the adjusted prevalence of class 3 obesity (BMI of at least 40) rose significantly for women (P = .01), but not for men.

Black women also were significantly more likely to be obese or severely obese, compared with non-Hispanic white women in the study, the investigators found. Among men, current smokers were less likely to be obese than never smokers, and women with education beyond high school were less likely to be obese than women who had not finished high school.

The investigators reported no funding sources and had no disclosures.