The restaurant and beverage industries have assailed the plan as misguided. They say the city's health experts are exaggerating the role sugary beverages have played in making Americans fat.
One board member, Dr. Sixto R. Caro, abstained from voting. The other eight board members voted yes.
"I am still skeptical. . This is not comprehensive enough," said Caro, a doctor of internal medicine who practices in Brooklyn and Manhattan.
Some New Yorkers have also ridiculed the rule as a gross government intrusion and tens of thousands signed a petition, circulated by the industry, voicing their opposition.
The unprecedented regulation would follow other ambitious health moves on Bloomberg's watch.
Some have proven to be national pacesetters, such as making chain restaurants post calorie counts prominently on their menus; McDonald's announced Wednesday that it would start displaying the information nationwide next week, before a federal requirement that could force all major chains to do so next year.
New York City also has barred artificial trans fats from restaurant food and taken aggressive steps to discourage smoking. Starting this month, dozens of city hospitals are asking mothers of newborns to listen to talks about why they should breast-feed instead of using formula.
Bloomberg and other advocates for the soda plan — who include a roster of doctors and such food figures as chef Jamie Oliver — see it as another pioneering step for public health.
After Thursday's vote, Bloomberg's official Twitter feed tweeted: "NYC's new sugary drink policy is the single biggest step any gov't has taken to curb (hash)obesity. It will help save lives."
They say the proposal strikes at a leading cause of obesity simply by giving people a built-in reason to stop at 16 ounces: 200 calories, if it's a regular Coke, compared to 240 in a 20-ounce size. For someone who drinks a soda a day, the difference amounts to 14,600 calories a year, or the equivalent of 70 Hershey bars, enough to add about four pounds of fat to a person's body.
Beyond the numbers, some doctors and nutrition experts say the proposal starts a conversation that could change attitudes toward overeating. While there are many factors in obesity, "ultimately it does come down to culture, and it comes down to taking some first steps," said Dr. Jeffrey Mechanick, a Mount Sinai School of Medicine professor who has studied the effect of government regulation on the obesity epidemic.
Soda makers and sellers say the plan unfairly singles out soft drinks as culprits for the nation's fat problem, represents an overweening government effort to regulate behavior and is so patchy as to be pointless. Because of the web of who regulates what, it would affect a belly-buster regular soda sold at a sports arena but not a 7-Eleven Big Gulp, for instance.
An average New Yorker goes to the movies about four times per year and buys concessions only twice, said Sun Dee Larson, a spokeswoman for the AMC Theatres chain.
"We firmly believe the choices made during the other 363 days have a much greater impact on public health," she said in a statement.
Thursday's vote is unlikely to be the final word on the proposal.
A soft-drink industry sponsored group called New Yorkers for Beverage Choices — which says it has gathered more than 250,000 signatures on petitions opposing the soda plan — is considering a lawsuit and exploring legislative options for challenging the plan.
"This is not the end," Eliot Hoff, a spokesman for the group, said in a written statement. "We will continue to voice our opposition to this ban and fight for the right of New Yorkers to make their own choices. And we will stand with the business owners who will be hurt by these arbitrary limitations."
It's not clear what legislative routes there may be: City Council Speaker Christine Quinn said Wednesday she's not interested in trying to block the expected health board vote, though she has said she isn't a fan of the soda idea.
The rule wouldn't apply to lower-calorie drinks, such as water or diet soda, or to alcoholic beverages or drinks that are more than half milk or 70 percent, unsweetened juice.
Enforcement would be conducted by an existing corps of city restaurant inspectors. A violation would lead to a $200 fine.