Picture this: A man swallows pack after pack after pack of sugar as two people sitting next to him watch incredulously.

Enjoying their lunch with 20-ounce bottles of no-name soda, they can’t believe their eyes and shake their heads in disbelief. The man ignores their stares, drunk with the task before him.

A tagline flashes on the screen: “You’d never eat 16 packs of sugar. Why would you drink 16 packs of sugar?”

The ad, an anti-soft drink spot from the New York City Department of Health, is the latest salvo in the decades-long war between critics of sugary beverages and the multibillion-dollar companies that produce them, including Coca- Cola and Pepsi, and the industry’s lobbying arm, the American Beverage Association.

Recent indicators that America’s expanding waistline is threatening to become a permanent epidemic — including a report projecting that more than one-third of Americans will be obese by 2030 — have intensified calls for the nation to lay off the sugar. That has put the bull’s-eye on the beverage industry, whose high-calorie drinks critics argue contribute to tooth decay, diabetes and heart disease.

The industry says it’s unfair to be the target of so much of the blame. Companies such as Coca-Cola and Pepsi point to the popularity of their low-calorie options, as well as their efforts to produce mid-calorie sodas and smaller cans of their full-calorie beverages.

The pressure from critics hit new heights Thursday when New York Mayor Michael Bloomberg announced a proposed ban on the sale of sodas and other sugary drinks larger than 16 ounces at restaurants, movie theaters and street carts. The measure is expected to go into effect as soon as next March in the nation’s largest metro area. Diet sodas, fruit juices, alcohol or drinks such as milkshakes are not included in the proposed ban. Grocery and convenience store sales also are excluded.

Also, the Center for Science in the Public Interest, which has waged a national campaign to tax sugary drinks, will have a first-ever “national soda summit” in Washington on Thursday and Friday to discuss the issue. A former Coke executive, whom the group declined to identify, promises to “tell the truth about ‘Big Soda’s’ marketing strategies,” the group said. A Coca-Cola spokesman said he did not know who it might be.

Industry is fighting back

In a statement Thursday about New York’s proposed ban, Atlanta-based Coca-Cola said, “New Yorkers expect and deserve better than this. They can make their own choices about the beverages they purchase. We hope New Yorkers loudly voice their disapproval about this arbitrary mandate.”

The American Beverage Association, channeling former President Ronald Reagan, said, “There they go again. The New York City Health Department’s unhealthy obsession with attacking soft drinks is again pushing them over the top. The city is not going to address the obesity issue by attacking soda, because soda is not driving the obesity rates.”

The association, feeling the pressure ratcheting up, already had created a recent national “Delivering Choices” campaign, including a TV spot pointing to the low- or no-calorie options most brands have added to vending machines across the nation.

The brands point to a study in the American Journal of Clinical Nutrition that found, between 1999 and 2010, sugar consumption from sodas decreased 39 percent, while obesity rose 7 percent.

In addition, they tout the millions they have donated to children’s activities, the creation of parks and education programs on healthy lifestyles.

Attacks grow louder

The battle could prove pivotal. U.S. sales of soft drinks — the bread and butter of the nonalcoholic refreshment segment — have been sliding since their peak in 1998, industry data show. A driving force has been Americans’ concern about their sugar intake, which has led many to switch to water, juices, teas, coffees and milk as replacements.

Pepsi leaders said 49 percent of their drinks are juices, low-calorie, diet or sports drinks, while Coca-Cola puts its number at about 41 percent.

Soda sales, while declining, still make up the lion’s share of the industry’s income. About 75 percent of the nonalcoholic beverage industry is made up of megabrands — those trademarked drinks with sales of 100 million 192-ounce cases, according to Beverage Digest, an industry publication. Of those, almost half are carbonated soft drinks.

“Over the last decade, the calories Americans consumed in soft drinks have dropped substantially — about 21 percent,” said John Sicher, Beverage Digest’s editor and publisher. “If you look at this realistically, the biggest problem is lifestyles. Americans are more sedentary.”

Still, the drumbeat to slim down the nation has been loudest when the discussion turns to ridding Americans of sugary drinks. While reducing consumption of fast food, salty chips and sugar-laden cereals has been offered as a solution to the nation’s weight problem, none has galvanized as much support as soft-drink bans.

“I saw it begin to rise in the ’80s, but it wasn’t near the decibel levels it is today,” said Rhona Applebaum, a vice president and chief scientific and regulatory officer at Coca-Cola, who wrote a guest editorial this past Monday defending the industry.

Some of the calls have been part of comprehensive attacks on obesity.

First lady Michelle Obama has called for advertisers to increase promotion of healthy foods while decreasing the prominence of sugary snacks and drinks on TV.

HBO’s recent documentary series “Weight of the Nation” spotlighted the country’s heath crisis, including a focus on sodas and other high-calorie drinks in children’s diets.

Others have zeroed in on issues with sugar-sweetened beverages.

The Centers for Disease Control and Prevention’s National Center for Health Statistics reported last August that consumption of sugary drinks — a category that includes all beverages, not just carbonated — has increased in the United States for both children and adults over the past 30 years. The report said on any given day, about half of the population over the age of 2 consumes a sugary drink.

In a podcast on Yale University’s Rudd Center for Food Policy and Obesity, Steven Gortmaker, a health sociology professor from Harvard University, said, while sugary drinks may not be the biggest contributor to obesity in the country, their impact is significant, especially consider that the average high school male consumes 350 to 400 calories a day in the category.

“While that may be only part of our daily caloric needs, it’s a huge number,” he said in April. “It’s, in fact, a number that’s large enough to be easily driving and causing the obesity epidemic.”

Cities such as Boston have moved to ban soft drink sales on municipal property, while six states have levied some form of excise taxes on the industry.

Kelly Brownell, director of the Rudd Center, said sugary sodas attract the obesity focus because they don’t hold nutritional value. He said New York City’s move could be important, because it could influence other metro areas to follow in its footsteps.

Marketing’s role

George Hacker, senior policy adviser for health promotion for the Center for Science in the Public Interest, said the beverage industry has made strides in reducing the calories in its drinks overall. But it still focuses most of its U.S. marketing muscle on best-sellers such as Coke, Pepsi and Mountain Dew.

Because the full-calorie drinks are among their best-sellers and where they make the most money, the companies also spend more money promoting them.

That is most evident, he said, on grocery and convenience store shelves, where the full-sugared soft drinks command the largest percentage and most prominent positions — at eye level, where most purchases occur.

“Even when they promote their diet sodas or their intermediate sodas, they are still promoting the brand name and normalizing the consumption of their drinks,” he said.

Coca-Cola leaders disagreed. They said two of their best-sellers in the U.S. — Diet Coke and Coke Zero — reduce calories and offer consumers an option that many are taking. Diet Coke became the nation’s No. 2 best-selling soft drink (behind Coke) last year — surpassing full-flavored Pepsi — and Coke Zero has been a hit for Coke, growing 12.4 percent in 2011.

Dave DeCecco, a spokesman for Pepsi, said there is no agenda on store shelves to guide consumers to one drink or another. The company puts all its best-selling products — full sugar or reduced — where consumers can get them because of demand.

“That’s a factor of consumers making a choice of what they want,” he said. “It is just as easy to find a Diet Pepsi in stores as it is to find Pepsi.”

Both companies also are working on mid-calorie sodas that mimic the full flavor of their brands while eliminating much of the sugar. Pepsi introduced Pepsi Next earlier this year, while Coke is testing mid-calorie Fanta and Sprite in a handful of cities, including Atlanta.

Time to talk?

Industry leaders said part of the problem is a lack of open dialogue. They point out that the Center for Science in the Public Interest has rebuffed their request to speak at its “soda summit” this week.

Jeff Cronin, a spokesman for the group, acknowledged that the meeting is closed to the beverage companies and their allies.

“The soda industry was purposefully excluded from this conference,” he said.

Applebaum said she welcomes a discussion about obesity and the role that everyone plays in it, including Coca-Cola. But she said it has to be realistic and the focus put on how to improve health, not pointing fingers.

“To me, this is just another ploy to try to demonize a product and create a scapegoat when what we should be doing is coming up with solutions,” she said.