“Sin taxes” on cigarettes have turned out to be the most effective weapon in the campaign to reduce smoking.

Why not try it on Flamin’ Hot Cheetos, vanilla Coke and Twinkies?

With increasing vigor, public health experts and think tanks are calling for extra taxes on foods and drinks that are heavy in calories and light on nutrition. New York Gov. David Paterson proposed an 18% soda tax last year as a budget-balancing measure, only to abandon it three months later in the face of stiff public opposition. Lawmakers in at least five other states have gone on the record in support of the idea.

Junk-food taxes are often mentioned as a way to help fund a restructuring of the healthcare system, though no one in Congress has endorsed them.

The notion is catching on with the general public, however. A Kaiser Family Foundation poll last month found that 55% of respondents favored a tax on unhealthful snack foods, up from 52% in April. Support for a soda tax rose to 53% from 46%.

And 63% of those who opposed the idea said they would change their minds if the revenue were used to fund healthcare reform and combat health problems related to obesity.

A report this summer from the Urban Institute said such taxes are needed to ensure that rising obesity rates don’t cause the average American life expectancy to fall for the first time in history.

“We are killing 100,000 people per year, so something needs to get done,” said University of Virginia pediatric cardiologist Arthur Garson, one of the study’s authors.

Many citizens object to such “nanny state” attempts at social engineering.

“This is the most ridiculous idea I’ve heard,” said Kellie Glass, a registered dietitian in Ashland, Ky., who doesn’t care to be penalized for indulging in ice cream now and then. “Folks are just not going to give up all the foods they love, even if they are more expensive.”

Junk-food taxes are also unfair, because the poor would be hardest hit, said fiction writer Julie Cochrane of Marshall, Va.: “I am not about to raise taxes on a single mom scraping by on a low-wage job.”

Still, the logic of a junk-food tax seems clear. Fattening foods tend to be cheap, and fresh produce and lean cuts of meat are often the priciest. A tax could help offset that imbalance, nudging people to eat more of what they should and less of what they shouldn’t.

“This seems an absolute no-brainer to me,” said Kelly Brownell, director of the Rudd Center for Food Policy and Obesity at Yale University who has long promoted such taxes.

But research suggests it’s hardly that simple.

To make a significant dent in escalating rates of obesity, taxes would have to be steep and widespread. Two-thirds of states now impose a modest soft-drink tax -- the average rate is 5.2% -- and though the taxes are linked to a drop in body weight, the difference is extremely slight: about 3 ounces for a 5-foot-10, 279-pound person.

Taxes on foods such as candy bars and microwave popcorn are even less effective, according to available data.

There’s even evidence that such taxes can have the perverse effect of increasing consumption of fatty or salty foods.

There are reasons why taxes curb smoking but might have little effect on obesity.

Raise the cigarette tax, and smokers can either pay up or quit. Raise the tax on sugar-sweetened colas, however, and customers can switch to sports drinks or punch, which often contain even more calories.

Moreover, tobacco taxes apply to all products you can legally smoke. Junk-food taxes are less logical. A 5.5% snack tax in Maine, for instance, covered blueberry muffins and fresh-baked apple pies, but not English muffins or frozen pies.

Tobacco taxes are also much higher than anything likely to be adopted for food and beverages. Slapping a 10% tax on a $1.50-bottle of Coke would raise the price a mere 15 cents -- not enough to persuade most shoppers to drink Diet Coke instead. Many calorie-laden foods are simply too cheap to be priced out of the market by any but the most draconian of taxes.

Studies mostly bear this out.

Several economic studies based on the effects of actual price increases have concluded that a 10% tax on sodas, sports drinks and fruit juice cocktails would prompt consumers to reduce consumption by 8% to 11%. Some studies found that price hikes motivated people to switch to drinks such as milk, coffee and tea -- changes that in theory could reduce weight.

How meaningful is an 8% to 11% cutback? A clinical trial of 810 adults in May found that reducing soda intake by 100 calories a day was linked to half a pound of weight loss after 18 months.

Other studies failed to match those modest results.

For example, a trio of economists analyzed 16 years of U.S. household health data to study the feasibility of using a soft-drink tax to help Americans lose weight. In a 2008 paper, the researchers calculated that a 1-percentage-point increase in the tax would reduce the average body mass index by just 0.003 units.

In other words, an overweight person with a BMI of 27 would end up with a BMI of 26.997 -- still well short of the 20-25 range considered healthy.

Even a soft-drink tax increase of 20 percentage points wouldn’t help much, because soda accounts for only 7% of calories in the American diet.

Taxes on snack foods are likely to be even less effective.

A team from the U.S. Department of Agriculture contemplated a tax on salty foods such as cheese puffs and pretzels. But unless the tax topped 10%, it would translate into much less than 1 pound of weight loss a year, the researchers reported in 2004.

A 2007 paper titled “Cheap Donuts and Expensive Broccoli” used federal data to predict the effect of a 100% tax on all high-fat and low-nutrient foods. It concluded that even this unrealistically high tax would ultimately reduce BMIs by less than 0.2 points.

The experience of Maine’s 5.5% snack tax is particularly discouraging. Enacted to help close a budget gap, it lasted 10 years before it was repealed under pressure from angry voters. Despite the price hike on such items as ice cream, hot cocoa, cake, cookies and pudding, Maine’s adult obesity rate doubled from 10% to 20% while the tax was in effect.

The flip side of taxing junk food is subsidizing healthful foods. The Department of Agriculture has calculated that cutting prices of fruits and vegetables by 10% would increase consumption by 6% to 7%.

In the Changing Individuals’ Purchase of Snacks -- or CHIPS -- study, Minnesota researchers cut prices in half for low-fat snacks in 55 high school and office vending machines. Sales nearly doubled, the researchers reported in 2001.

In another experiment, cafeteria sales of fruit and salad tripled when prices were cut in half. In a third, a half-off sale on fruit boosted purchases by a factor of four.

California public schools began removing soda from vending machines in 2004, but it’s unclear whether students are any thinner -- especially because the machines still sell sports drinks that contain almost as much sugar, said Gail Woodward-Lopez, associate director of the UC Berkeley Center for Weight and Health.

Still, experts caution that government attempts to influence diet could have unexpected results -- especially when taxes are involved.

A 2007 British study used government data on household diets and food expenditures to predict the effect of extending the country’s 17.5% sales tax to various foods. When items high in saturated fat were slapped with the tax, the model estimated that deaths would rise by 1,800 to 4,000 a year because consumers would be prompted to switch to foods with more salt.

To fix that problem, the scientists ran a model in which the tax applied to all kinds of unhealthful foods. This time, deaths fell by as many as 2,500 a year, but cholesterol levels rose as people switched from salty foods to fatty dairy items.

And unfortunately, consumers in both scenarios did the last thing any anti-obesity crusader would want: Facing higher grocery bills, they bought fewer fruits and vegetables.

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karen.kaplan@latimes.com