Experts say there is strong evidence that those sticking to televisions and computers clean up childhood obesity, which increases the risk of illness
A lot of time on the screen can raise a dozen more deadly cancers, experts warn.
Medics say there is "strong evidence" that chat rooms, which are attached to televisions, computers and smartphones, promote childhood obesity.
They warn that children are more likely to become fatty adults who are at greater risk of developing 12 types of cancers.
Experts warn that screen time is rising all over the world – a disadvantage in terms of lifestyle, such as poor diet and inactivity.
The report of the World Cancer Research Foundation states that people who watch too many phones and gaze on their smartphones simply eat more than they burn.
And they have less chance of realizing that they are full when dishes are subjected.
Contacting malicious advertisements increases their chances of becoming fat.
Caroline Cerny of the Obesity Health Alliance said: "Too many unhealthy food and drink eating, with a sedentary lifestyle contributes to overweight and obesity – this is clear.
"We also know that when children spend time in front of screens, they are bombarded with malicious food ads.
"This new report highlights the threat of unhealthy lifestyles and children's exposure to advertising.
"We need 21:00 water coverage for TV food and similar online restrictions."
About two out of three adults are now overweight or obese.
The report warns about excessive consumption of sugar drinks and undesirable food also increases obesity, increasing the risk of cancer.
Researchers said they have "string evidence" Britons can reduce their chances of being fat while staying active and eating Med diet and plenty of fiber. The study also found that breast-fed children were less prone to obesity.