Saving the world one tax at a time might sound like a silly notion. Not to those who want a soda tax to control people's consumption habits in the name of fighting obesity.

On ABC's April 8 "World News with Charles Gibson," John Berman reported that soft drinks were making people fat - something you don't see in soft drink advertisements.

"If you watch the commercials, soft drinks make us sing, soft drinks make us smile," Berman said. "But researchers say they also make us fat."

So, to address this problem, Berman consulted Kelly Brownell, director of the Rudd Center for Obesity at Yale University who agreed.