* Rules apply to drive-through windows

* Regulations take effect Nov. 10, 2010

By Jason Szep

BOSTON, May 13 (Reuters) - Massachusetts approved the toughest statewide restaurant menu labeling rules in the United States on Wednesday, requiring major chain restaurants to display the calorie content of the food they sell.

The regulations, designed to combat rising obesity, are more comprehensive than those in California, which in September became the first state with menu labeling rules for fast-food restaurant chains such as McDonald's Corp (MCD.N: Quote, Profile, Research) and Yum Brands'(YUM.N: Quote, Profile, Research) KFC, advocates of healthy foods say.

Approved by the Massachusetts Public Health Council, the rules will require restaurant chains with 20 or more in-state locations to post calorie counts next to each item on their menus or menu boards, including those at drive-throughs.

The requirements take effect Nov. 1, 2010, and will apply to 50 restaurant chains with a combined 5,800 locations.

"This is a major step in the right direction in fighting the obesity epidemic in our state," Massachusetts Department of Public Health Commissioner John Auerbach said in a statement.

More than half of the adults in Massachusetts are overweight or obese, according to a 2008 state report that also showed adult obesity more than doubling in 20 years. About 33 percent of Americans are overweight, while more than 34 percent are obese, according to U.S. government figures.