Most young people in the UK are unaware of the serious damage junk food can do to their health, a survey suggests.
The British Heart Foundation poll found 73% of eight to 15-year-olds were not aware that a junk food-laden diet could potentially shorten their life.
Instead, 45% thought the worst that could happen was that they would put on weight, develop tooth problems, get spots or become unpopular.
Two thirds of children are predicted to be overweight or obese by 2050.
Today's junk food generation can't see beyond the burger box
Mike Knapton British Heart Foundation
At present, almost a third of 10 and 11-year-olds are currently overweight or obese.
It is feared that today's children may be the first generation who live shorter lives than their parents.
However, the BHF survey, of 1,100 children, found that 56% confidently predict they will live to be over 80, and 11% believe they will live to more than 100.
Ryan Bolton, 11, from Walsall said: "I know that eating junk food can give you spots and make you put on weight but I'm not really bothered about anything else. The future is too far off to worry about it."
The charity released an online game, called Yoobot, to help children make healthier food choices.
Users create a mini version of themselves - the Yoobot, and then discover how exercise and diet impacts on life expectancy and wellbeing.
Once created, the Yoobot does not just live on the website, it also talks to its creator throughout the day using SMS and email.
It will complain if it's hungry, ask for junk food and generally make itself a part of the user's life.
Mike Knapton, BHF director of prevention and care, said: "Today's junk food generation can't see beyond the burger box.
"They are missing the fact that eating unhealthily can have dire consequences on their long-term health.
"The Yoobot is an innovative way for children to explore the effects of eating a diet of junk food. The clock is ticking on the obesity time bomb and it is now more important than ever for children to be educated enough to take control of their diets."
Dr Ian Campbell, medical director of the charity Weight Concern, said: "We have made progress in making young people more aware of the importance of a healthy diet and active lifestyle.
"But what we need to do now is to reinforce the link between lifestyle and health, not just weight but quality of life and life expectancy too.
"Ensuring the message is in on the right wavelength for youngsters is key, and this web-based programme can help us to achieve that.
"Young people will only change their lifestyle when they have a good reason to do so; it's important that we help them find those reasons."
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