Children and teenagers who spend lots of time in front of screens---especially TVs---are   easier to get more weight as they grow, according to a new study. The findings agree with the research suggesting all that inactive sitting and always watching   advertisements may lead to poor eating habits. Researchers used results from a long-term study of children who took part in the surveys every two years. Children were between ages 9 and 16 when the study started. Out of 4,300 girls in the   study, 17 percent were overweight or obese . Twenty-four percent of the 3,500 boys   were also above a healthy weight. The surveys included questions about their height and weight as well as how much time they spent watching TV and DVDs and playing computer and video games. From one survey to the next, each one-hour increase in children's daily TV watching was in connection with an increase of about 0.1 points on a body mass index (BMI) , which measures weight in connection with height. There's an increase of about half a pound in weight per extra hour of TV. "The weight of the evidence is so strong that television watching is connected with unhealthy changes in weight among youth," says Jennifer Falbe, who led the study while at the Harvard School of Public Health in Boston. "It's important for parents to know that all the obesity-causing screens really should be limited in their children's lives." Falbe says. "When children watch TV, there are many food advertisements on TV that might lead them to eat a cookie or drink a soft drink." What's more, she says, "they can get into a hibernating  state on the sofa, even if children are sitting down while playing a computer game." How many children took part in the study?
4,300 3,500 7,800 9,800