They say 'the camera adds 10 pounds', and in the case of kids' cartoon characters, they may well be right. Cuddly-looking, well-rounded cartoon characters are a staple of the TV medium, with everyone from Fred Flintstone to Homer Simpson and the Peppa Pig family adopting a familiar ovoid appearance that makes them appear humorous, relatable, and friendly.

But a new study suggests that the portly appearance of these popular cartoon characters could also be having a negative impact on what children eat. Researchers at the University of Colorado Boulder in the US have found that kids aged between 6 and 14 years old consume significantly higher amounts of high-calorie junk food like cookies and candy after observing overweight cartoon characters.

More than 300 volunteers took part in the experiment, with the researchers looking to investigate whether children exhibit behavioural priming effects from being exposed to a stereotypically overweight character. In the course of the testing, some children were shown a healthy weight cartoon character, some were shown an overweight cartoon character, and others weren't shown any cartoon characters at all.

After the visual prompts, they were given free access to high energy, low-nutrient snack foods, to see if the exposure to the cartoon images acted as a priming agent. The results, published in The Journal of Consumer Psychology, showed a significant increase in food intake.

According to Margaret C. Campbell, lead author of the study, children shown the overweight cartoon characters were primed to the overweight stereotype, which affected their eating behaviour.

"They have a tendency to eat almost twice as much indulgent food as kids who are exposed to perceived healthier looking cartoon characters or no characters at all," she said in a press release.

Even kids who were exposed to both healthy and overweight cartoon characters displayed a tendency to eat more than children who didn't see the overweight character, suggesting the appearance of the overweight stereotype is enough to provoke children to snack more heavily.

However, the children's indulgent eating was moderated when their previous knowledge of healthy food and eating practices was called to mind directly before they were given the option of eating cookies.

The good news then is that the research shows most kids do in fact know the right things to eat - but a timely reminder may be crucial to help keep them on the right track.

"This is key information we should continue to explore," said Campbell. "Kids don't necessarily draw upon previous knowledge when they're making decisions. But perhaps if we're able to help trigger their health knowledge with a quiz just as they're about to select lunch at school, for instance, they'll choose the more nutritious foods."