A study, by Stanford University, which examined the data from the National Health and Nutrition Examination Survey (NHANES) correlated a sharp decrease in physical exercise to an increase in average body mass index (BMI) while the calorie intake remains the same.
The research published in the American Journal of Medicine reveals that in the past 20 years there has been a drastic change in the exercise rate for both women and men. The study points the finger at the lack of exercise as the culprit for the epidemic obesity rate that currently characterizes the U.S.
The data reveals that over the last 20 years the number of US adult women who reported no physical activity jumped from 19.1% in 1994 to 51.7% in 2010. For men, the number increased from 11.4% in 1994 to 43.5% in 2010. In the same period, the average BMI has increased across the board, with the most dramatic rise found among young women ages 18-39.
“These changes have occurred in the context of substantial increases in the proportion of adults reporting no leisure-time physical activity, but in the absence of any significant population-level changes in average daily caloric intake,” explains lead investigator Uri Ladabaum, MD, MS, Associate Professor of Medicine (Gastroenterology and Hepatology), Stanford University School of Medicine. “At the population level, we found a significant association between the level of leisure-time physical activity, but not daily caloric intake, and the increases in both BMI and waist circumference.”
The study did not investigate what type of food was consumed and just looked at caloric intake versus exercise and its correlation to obesity. The researchers also examined the increase in abdominal obesity, which is viewed as an independent risk factor for metabolic syndrome and has been associated with a decreased mortality rate even in people with normal BMI. Abdominal obesity was defined by waist circumference of 88 cm (34.65 in) or greater for women and 102 cm (40.16 in) or greater for men. Data showed that average waist circumference increased by 0.37% per year for women and 0.27% per year for men. Just like the rise in average BMIs, the group most affected by increased rates of abdominal obesity was women.
“The prevalence of abdominal obesity has increased among normal-weight women and overweight women and men,” observes Dr. Ladabaum. “It remains controversial whether overweight alone increases mortality risk, but the trends in abdominal obesity among the overweight are concerning in light of the risks associated with increased waist circumference independent of BMI.”
“Our findings do not support the popular notion that the increase of obesity in the United States can be attributed primarily to sustained increase over time in the average daily caloric intake of Americans,” concludes Dr. Ladabaum. “Although the overall trends in obesity in the United States are well appreciated and obesity prevalence may be stabilizing, our analyses highlight troublesome trends in younger adults, in women, and in abdominal obesity prevalence, as well as persistent racial/ethnic disparities.”
The managing editor of the American Journal of Medicine highlighted the role of the community in general to promote health behavior. “If we as a country truly want to take control of our health and our health care costs, the Ladabaum et al paper should be our clarion call. From encouraging communities to provide safe places for physical activity to ensuring ample supply of healthy food to empowering Americans to take control of their health, we must launch a concerted comprehensive effort to control obesity,” said Pamela Powers Hannley.
Pamela Powers Hannley. Move More, Eat Less:It’s Time for Americans to Get Serious about Exercise. The American Journal of Medicine, 2014; DOI: 10.1016/j.amjmed.2014.05.026
Uri Ladabaum, Ajitha Mannalithara, Parvathi A. Myer, Gurkirpal Singh. Obesity, Abdominal Obesity, Physical Activity, and Caloric Intake in U.S. Adults: 1988-2010. The American Journal of Medicine, 2014; DOI: 10.1016/j.amjmed.2014.02.026