The Olympic Summer Games -- the quadrennial sports and advertising extravaganza -- are now underway. Once again, we'll be thrilled (and perhaps even inspired) by the graceful gymnasts, the lightning-fast sprinters, and the seemingly inexhaustible swimmers.

Less thrilling is the endless drumbeat of ads from long-time sponsors Coca-Cola (since 1928) and McDonald's (since 1976). Their ads are too clever to nag you to fill up on Big Macs and large Cokes. Instead, they worm their way into your heart to create warm, fuzzy feelings.

Companies love to sponsor the Olympics. They reach millions of eyeballs with their seductive TV ads, and they know that some of the squeaky clean, healthy images of star athletes will rub off on their sooty reputations.

How ironic! The global event that showcases the fittest people on the planet is bankrolled -- to the tune of about $4 billion -- by companies whose foods undermine our health. Major sponsors pay roughly $100 million and provide 40 percent of Olympics revenues. And that won't change until at least 2020. But the obesity epidemic is leading some to recognize the irony:

• The London Assembly urged the International Olympic Committee (IOC) to adopt criteria for sponsors that would bar companies like McDonald's and Coca-Cola.
• The Academy of Medical Royal Colleges said that McDonald's and Coca-Cola's sponsorship "sends out the wrong message" to children.
• The Lancet, the premier British medical journal, lamented, "Harder to erase will be the long-term effect of Games-associated junk food advertising on people's hearts and waistlines -- definitely one Olympic legacy the world can do without."
• Even the IOC president, Jacques Rogge of Belgium, acknowledged a problem.

Of course, the companies have silky-smooth retorts. A Coke spinmeister said, "We believe all of our drinks can be enjoyed as part of an active, healthy lifestyle." McDonald's said, "Many athletes tell us we are their favorite place to eat."

The next summer games will be held in Rio de Janeiro in 2016. Brazilians are one of the world's biggest consumers of soda (fueled by Coca-Cola's billion-dollars-a-year investments), and host to over 650 McDonald's outlets. Experts predict that Brazil's bulging waistlines may grab the world record from the United States by 2022. Will junk-food marketers get an Olympic carte blanche again?

I hope that the four-year breather will give Olympic officials and companies time to work out a deal: If you want to link your brand names to the games, you may only promote and sell your healthier products.