At least once a week millions of children will play an game on the Internet that also displays an advertisement, mostly for snacks or candy, a Dutch behavioral scientist has found. It will probably not a be a surprise to learn that playing these advergames affects kids' behavior: specifically, it gets them to eat more candy.

After playing a game with an embedded food advertisement, children ate 55% more of the candy offered them (16 extra M&Ms) than children who had just played a game with an embedded toy advertisement, according to researcher Frans Folkvord. Moreover, it did not matter whether the advertisements were for candy or fruit: the 1000 children involved in the test ate more candy after playing a game involving food. Of course, that is also what they were offered.

While many parents worry over what their child is watching on the Internet, few understand that they're repeatedly getting candy and soda advertisements while playing games.

Many countries have tried to limit junk food advertisements to children. Perhaps the strongest measures are in the United Kingdom, which in 2006 put in place a total ban of junk food advertising around all children's programming, on all children's channels and programs designed to appeal to those under 16 years old.

Naturally, there was resistance among the companies who profit from sales to children. In 2012, Coca-Cola and McDonald's collaborated on one of the earlier advergames, Crabs and Penguins, a game you can still download today if you'd like to watch your child spend hours collecting soda bottle caps.

Children don't notice the advertisements. Only 6% recognize that these games contain advertisements, according to Folkvord, even when brand names and logos are clearly recognizable — such as the branded fast food restaurant they pass as they play. And unlike TV commercials, which last a mere 30 or 60 seconds, children can be exposed to these advertisements for hours at a time while they play the game.

Folkvord argues that there's a need to consider prohibiting food commercials aimed at children. He is collaborating with the University of Barcelona to formulate and submit such a recommendation to the European Union. As he pointed out in a statement, “Children play a game, get hungry and reach for treats. As the cycle continues, children fail to learn healthy eating behaviour. The results of my study indicate that these advertisements have an even heavier influence on children who are already overweight.”

Advergames are only one way that the food industry is fighting back against the idea that they bear some responsibility for why we are so fat (see the now-defunct Global Energy Balance Network). And while many parents worry over what their child is watching on the Internet, few understand that they're repeatedly getting candy and soda advertisements while playing games.

Folkvord has also co-authored a newly published review article on marketing to children and eating behavior. One of its conclusions is that manufacturers' promises to decrease their advertising to children are of no value — one more reason to consider banning them.

The review article appears in Current Opinion in Behavioral Sciences.