Big Soda may have triumphed over Big Public Health last week in the latest battle over Mayor Nutter's proposed tax on sugary drinks. But don't expect the idea to dry up like some sticky puddle of spilled Coke. It may not make soft-drink distributors, retailers, and truck drivers happy. But it makes too much sense for the rest of us.

I'm kidding about "Big Public Health," of course, even if "Big Soda" richly deserves the label Nutter plastered on it. All around the country, the soft-drink industry and its allies have spoken with one voice - and loads of money - to defeat proposals for taxing high-calorie, largely nutritionless beverages, framing them as attacks on freedom and the march of the "nanny state."

Big Soda stopped a New York plan in 2008, and the next year it scared off Congress from taxing sugary drinks to help pay for covering the uninsured. Twice now, it has kept Nutter from gaining majority support on City Council for a sugary-drinks tax - even though this time it meant agreeing to a property-tax increase instead to help plug a huge hole in the school budget. Hardly a sure-fire way to appeal to your inner tea party.

Public-health advocates just don't have that kind of muscle. Rather than lobby, they're largely limited to the tools of persuasion - you know, things like data, research, and common sense.

That's why beverage-tax proponents such as Yale University's Kelly D. Brownell take the long view - and why Brownell wasn't disappointed after learning that Nutter had tried and failed again, just a year after his first attempt.

"Big Tobacco won out over public health the first couple of times, and then the dominoes began to fall," says Brownell, director of Yale's Rudd Center for Food Policy & Obesity and a professor of psychology, epidemiology, and public health.

For nearly two decades, Brownell has been making the case for taxing high-calorie, low-nutrition foods. He has lately turned his focus to sugary soft drinks, which he says have played an increasingly obvious role in the nation's obesity epidemic - especially since the mid-1990s, when they surpassed milk as the beverage most consumed by children ages 2 to 18.

Why the focus on soft drinks rather than junk food and other dietary pitfalls?

"They're the greatest source of added sugar in the American diet," Brownell says. "They're completely empty calories. I mean, even a Twinkie has some nutrition."

Brownell says study after study - especially ones not funded by the beverage industry - has shown the ill effects of sugary drinks.

Research suggests, for example, that people's bodies react differently to calories consumed in sweetened drinks than in food. Less sated by the sugary liquids than by solid food, they are more likely to consume additional calories beyond their basic needs.

One study of middle-school students found that every additional daily serving of a sugary drink increased obesity risk 60 percent. In other words, two Cokes a day - or Snapple or Gatorade - were enough to more than double the risk.

There are other ways, of course, to change public behavior. Cigarette use has undoubtedly been affected by aggressive public-health campaigns, and cities such as New York and Seattle are trying a similar approach to cut sugary-drink consumption.

But taxes are a reliable, time-honored method of reducing public harm that everybody must pay for - as Americans do for health-care costs related to obesity, which one recent study put at nearly $150 billion a year.

Classical economic theory has long accepted the notion of taxing certain items to cover shared costs - "externalities," in the language of the field, with pollution and tobacco as typical examples.

Justin Wolfers, an economist at the University of Pennsylvania's Wharton School, says sugary drinks belong on the list, too.

"Not that my drinking a soda makes me unhealthy," says Wolfers, a marathoner who actually needs the carbs in his occasional Gatorade. "But it imposes costs that we all may have to pick up."

Wolfers dabbles in the field of behavioral economics. And he uses a key behavorial insight - that people "are in a game with our future selves, and sometimes our current selves make bad decisions for our future selves" - to counter the complaint that a soda tax is overreaching nanny-statism.

"A lot of people just grow up thinking that soda is the beverage you have when you have a meal," Wolfers says. "But it's very likely that your future self would prefer that the government impose taxes to prevent your young dumb self from destroying the body that your future self will inherit, the same way that my future self would want higher cigarette taxes to prevent my current self from destroying my lungs."

For that matter, a sugary-drink tax can even claim an impressive economics pedigree. Brownell notes that Adam Smith himself, in 1776's The Wealth of Nations, lumps sugar in with rum and tobacco as unnecessary commodities "which are therefore extremely proper subjects of taxation."

A 2-cents-per-ounce tax on sugary drinks wouldn't stop anybody from buying soda that often sells dirt cheap for less than 11/2 cents per ounce. It won't destroy any businesses, or save the world. But the evidence shows it will cut sugar consumption and benefit public health, while adding a little useful cash to tax coffers, whether for obesity prevention or just to aid the schools.

It's a good trade-off. And the sooner we recognize that, the better.

Contact columnist Jeff Gelles at 215-854-2776 or jgelles@phillynews.com.