WHEN it comes to food fights, John Belushi's character in "Animal House" has nothing on Rick Berman. A prominent Washington lobbyist, Mr. Berman runs the Center for Consumer Freedom, a nonprofit advocacy group that is financed by the food and restaurant industries. Two months ago, after a report in a leading medical journal cast doubt on several assumptions about obesity, he pounced. His group ran $600,000 worth of full-page ads in a half-dozen newspapers, gloating that the study showed that obesity was not an "epidemic" but rather a lot of hype. "Americans have been force-fed a steady diet of obesity...