It's believed that San Francisco would be the first place in the U.S. to require such a warning on ads for soda if it receives a second approval from the Board of Supervisors next week and the mayor does not veto it.
John Maa, a general surgeon and member of the board of the American Heart Association in San Francisco, which lobbied for the ordinance, said advocates will seek to expand the warning requirement beyond the city.
Efforts to push a statewide warning requirement failed this year as did a city ballot measure last year to impose a tax on sugary drinks.
"Another attempt at the sugar-sweetened beverage tax is being considered," he said.
The ordinance would require the warnings on print advertising within city limits —billboards, walls, taxis and buses. It would not apply to ads appearing in newspapers, circulars, broadcast outlets or on the Internet.
The ordinance defines sugar-sweetened beverages as drinks with more than 25 calories from sweeteners per 12 ounces (340 grams). It requires warnings for other sugary drinks such as sports and energy drinks, vitamin waters, iced teas and certain juices that exceed the 25-calorie limit.
Liquid sugar is the new tobacco, as far as public health advocates are concerned. Berkeley approved a soda tax last year, the first in the country to do so. Davis, a college town, is requiring restaurants to serve milk and water as the default drink for children's meals.
About 32 per cent of children and teens in San Francisco are overweight or obese, according to a 2012 study by the California Center for Public Health Advocacy and the UCLA Center for Health Policy Research.
"This is a very important step forward in terms of setting strong public policy around the need to reduce consumption of sugary drinks; they are making people sick, they're helping fuel the explosion of Type 2 diabetes and other health problems in adults and in children," said Scott Wiener, one of three San Francisco supervisors pushing the legislation.
The label for billboards and other ads would read: "WARNING: Drinking beverages with added sugar(s) contributes to obesity, diabetes, and tooth decay. This is a message from the City and County of San Francisco."
Soda cans and bottles would not carry the warning.
Supervisors approved the proposal with an 11-0 vote requiring the warning, as well as two other measures aimed at curbing sugary drink consumption.
One proposal would prohibit soda ads on city-owned property, much like San Francisco does with tobacco and alcohol. Another would prohibit city funds from being used to buy soda.
Ryan Brooks, spokesman for Outfront Media, said it's not fair to single out billboards while exempting newspapers and magazines. The company has about 300 billboards and wall spaces that would be affected.
"It's all these people who are telling me how to live my life and raise my children. I make that decision, not a bunch of elected officials," he says. "Let's fix the homeless issue, let's fix potholes before you start telling me how to live my life."
Mayor Ed Lee has said through a spokeswoman that he is open to educating people through warning labels on advertisements.
Opponents have said it's not fair to single out billboard advertising or sugary drinks.
Roger Salazar, a spokesman for CalBev, which represents the state beverage industry, said the organization might sue to block the ordinance.
"Aside from being bad public policy, there are some free speech issues," Salazar said. "We're going to explore all of our options."