Girls and young women who devote much time to the Internet, get too little sleep or regularly drink alcohol are more likely than their peers to put on excess weight, a new study suggests.
The researchers, who followed more than 5,000 girls between 14 and 21 years old for 1 year, found that the more spare time girls spent on the Internet, the more their body mass index (BMI) increased.
Similar patterns were seen when the researchers looked at alcohol consumption and sleep. In the latter case, lack of sleep was linked to greater gains in BMI -- a measure of weight in relation to height.
The findings, reported in The Journal of Pediatrics, add to evidence implicating each of these three habits in promoting weight gain.
The effect of each may be small, but over time the pounds can add up, according to the researchers, led by Dr. Catherine S. Berkey of Brigham & Women's Hospital and Harvard Medical School in Boston.
The study involved 5,036 girls and young women who were surveyed regarding the number of recreational hours per week they spent on the Internet, which ranged from 1 to 5 hours, to 16-plus hours, as well as how long they typically slept each night (anywhere from 5 hours or less, to 9 hours or more) and how much alcohol they usually drank (ranging from none to two or more drinks per week).
In general, the researchers found, as Internet use climbed, so did BMI, particularly among girls younger than 18 years old.
When it came to sleep, those who clocked 5 hours or less tended to gain more weight than those who got a standard 8 hours. And girls and women who had 2 or more alcoholic drinks per week put on more pounds than those who drank the least.
The effects over 1 year were modest, Berkey's team points out. For example, a 19-year-old of average weight and height would gain 4 pounds if she were in the high-risk groups for Internet use, sleep and alcohol consumption.
However, the researchers add, over time that could translate into significant weight change.
Spending hours on the Internet likely contributes to weight gain by taking time away from physical activity, according to Berkey's team.
Lack of sleep may make people too tired to be active during the day; sleep deprivation also affects hormones and metabolism in a way that might promote weight gain.
Meanwhile, alcohol contains a significant amount of calories, and research suggests that people usually don't make an adjustment for liquid calories by eating or drinking less throughout the rest of the day.
SOURCE: The Journal of Pediatrics, July 2008.