Waistline of US Adults Continues to Expand, Report

A study reveals that an average U.S. adult's belly has expanded by more than an inch in the recent decade.

Sedentary lifestyle, along with the intake of unhealthy diet, is to be blamed for the expanding waistline. It has been noted that over the last 20 years there has been a dramatic drop in physical activity and a sharp rise in average body mass index. This drop in leisure time physical activity, especially among women, is to be blamed for the upward trend in obesity rate.

The recent study by the Centers for Disease Control and Prevention (CDC) reported that from 1999-2012, there has been a sharp rise in the rate of abdominal obesity and average waist circumference among American adults. 

The authors wrote, "Previous analyses of data from NHANES show that the prevalence of obesity calculated from body mass index (BMI) did not change significantly from 2003-2004 to 2011-2012. In contrast, our analyses using data from the same surveys indicate that the prevalence of abdominal obesity is still increasing. The reasons for increases in waist circumference in excess of what would be expected from changes in BMI remain speculative, but several factors, including sleep deprivation, endocrine disruptors, and certain medications, have been proposed as potential explanations."

According to the reports, waist circumference is a simple measure of total and intra-abdominal body fat. Although a rise has been witnessed in the rate of abdominal obesity in the U.S. through 2008, the trend in the recent years remains unknown. 

The study led by Earl S. Ford, M.D., M.P.H, of the CDC based this finding on the evaluation of the data retrieved from seven 2-year cycles of the National Health and Nutrition Examination Survey (NHANES) starting with 1999-2000 and concluding with 2011-2012. This data was used to determine the trend in the average waist circumference as well as the prevalence of abdominal obesity among American adults.

Abdominal obesity is when the waist circumference is more than 40.2 inches in men and greater than 34.6 inches in women.

Data of 32,816 men and non-pregnant women aged 20 years or older was evaluated. They noticed that the age-adjusted average waist circumference increased significantly from 37.6 inches in 1999-2000 to 38.8 inches in 2011-12. In men, the significant increase was of 0.8 inch, women 1.5 inch, non-Hispanic whites of 1.2 inch, non-Hispanic blacks 1.6 inch and Mexican American 1.8 inch.

In 1999-2000, the abdominal obesity increased from 46.4 percent to 54.2 percent in 2011-2012.  The increase was more in men i.e. from 37.1 percent to 43.5 percent, in women it increased from 55.4 percent to 64.7 percent, in non-Hispanic whites from 45.8 percent to 53.8 percent, in non-Hispanic blacks from 52.4 percent to 60.9 percent and in Mexican Americans it changed from 48.1 percent to 57.4 percent.

"Our results support the routine measurement of waist circumference in clinical care consistent with current recommendations as a key step in initiating the prevention, control, and management of obesity among patients," researchers explain.

The finding was reported in the September issue of JAMA.