Researchers say junk food advertising needs tighter controls. 

A paper has found children aged 2 to 17 see twice as many ads for unhealthy food than healthier options. 

The authors want limits on online ads for unhealthy food - and a ban on using cartoon characters in packaging. 

Co-author Lisa Te Morenga says such advertising intensifies the desire children already feel for junk food - and the constant barrage of ads makes children want it more.

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