Young and obese? Blame it on sedentary lifestyle

Cutting down on calories alone may not help you trim your bulging waistline as researchers have found that lack of leisure-time physical activity is linked to increased obesity, particularly in young women.

Researchers analysing data from the National Health and Nutrition Examination Survey (NHANES) in the US found that in the past 20 years there has been a sharp decrease in physical exercise and an increase in average body mass index (BMI), while caloric intake has remained steady.

"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," said Uri Ladabaum, associate professor at Stanford University School of Medicine in the US.

The number of US adult women who reported no physical activity jumped from 19.1 percent in 1994 to 51.7 percent in 2010.

For men, the number increased from 11.4 percent in 1994 to 43.5 percent in 2010. During the period, average BMI has increased across the board, with the most dramatic rise found among young women ages between 18 and 39 years.

The study looked at the escalation of obesity in terms of both exercise and caloric intake.

The study appeared in American Journal of Medicine.