New York City Mayor Michael Bloomberg is wading into the debate about how best to combat obesity by proposing a plan that would force restaurants, movie theaters, and street carts to stop serving sodas and other sugary drinks larger than 16 ounces. The plan, unveiled by Bloomberg’s administration Wednesday, does not include diet sodas, juices, and dairy products like milkshakes. Consumers would still be able to purchase larger sizes in grocery and convenience stores. The proposal, which could take effect as early as March 2012, will have to be approved by the city’s health department, though most believe the panel will sign off on it because they are appointed by the mayor. A soda industry spokesman decried the plan as unfairly targeting soft drinks.