The TV news story was probably a mangled version of some research by Chris Goodall that was just published and is making its way through the news machine.
Goodall was making a point about what a grotesquely large amount of carbon is released into the atmosphere in beef production, which is hugely energy-intensive. It also involves feeding grain to grass-eaters, which exacerbates the, production of, er, digestive methane. Goodall points out how environmentally grotesque this is by pitting a car against a walker, and demonstrating that, for a given distance, the walker's carbon footprint is four times larger than the car's -- if she replaces the calories she exerted with beef.
A vivid illustration! Strangely, the beef and the carbon fell out of the picture before the story got to television news, and now it's about driving being better than walking. About as twisted a misrepresentation as could be imagined (but all too easy to imagine, at the same time . . . )
An article:
http://tinyurl.com/2hfxme