How much TV children watch accurately predicts whether they will go on to become overweight, a study suggests.
It has previously been shown television is linked to weight gain as children are less active and eat while watching.
Researchers at New Zealand's University of Otago looked at how much TV children aged five to 15 watched.
The International Journal of Obesity study found the 41% who were overweight or obese by the age of 26 were those who had watched most TV.
A study by the same team published last year suggested children should watch no more than two hours of TV a day to protect their future health.
A BMI of 25 or over is considered overweight, and one of over 30 obese.
All the 1,000 children studied were born between April 1972 and March 1973.
At age five, seven, nine and 11, parents were asked how much TV they watched. At ages 13 and 15, the teenagers themselves were questioned.
Between the ages of five and 15, children were found to watch an average of 2.33 hours of TV per weeknight.
Aged 13 to 15, they watched an average of 24.6 per week.
At each age, the amount of TV watched was consistent with the child's BMI.
The links were stronger in girls, which the researchers say may be linked to the differences in lifestyle and physical make-up of between teenage boys and girls.