To celebrate our victorious Olympic athletes, how would you like a free fitness tracker with your ... Happy Meal?

That's what McDonald's offered, until reports came in that they caused skin irritation (one mom posted a picture of a red spot on her child's arm that happened after wearing the band for eight minutes; it was shared online over 100,000 times).

McDonald's went from the frying pan into the fire — or, more appropriately, the deep fryer.

But such marketing missteps don't keep fast-food companies, cereal makers, and snack manufacturers from targeting kids, and for one reason: Marketing food to children works.

For a recent study, researchers monitored brain activity in kids ages 8 to14 before and after seeing food commercials.

It turns out that an area in the kids' brains associated with reward and value (the ventromedial prefrontal cortices) is "significantly more active after watching food commercials."

And what does that add up to? Well, since 1980, when Congress removed the Federal Trade Commission's authority to restrict food advertising, the incidence of obesity has more than doubled in children and quadrupled in adolescents.

Fortunately, research also indicates that you can counter marketing campaigns by talking to your kids about the thousands of TV ads they see — what's being sold, what the motive is, and how not to be swayed by bogus ads.

If you take time to educate your kids, they'll be able to enjoy a healthier, more productive future.