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updated 12/13/2010 7:06:00 PM ET 2010-12-14T00:06:00

Taxing soda and other sweetened drinks may lead to only minimal weight loss among most people, according to a new study.

Over the course of a year, a tax that would raise the price of soda by 20 percent would lead people in middle-income households to lose about 1.5 pounds per year, the study found. Those in the uppermost and lowermost 25 percent of households in terms of income would see virtually no weight loss.

However, health policy makers should not discount this improvement when considering taxes on sweetened drinks as a means of improving health and raising revenue to offset budget deficits, the researchers said.

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"With these taxes, you raise a couple billion dollars. If that revenue is used productively, it might generate more of a positive effect than the tax itself," said study researcher Eric Finkelstein, associate professor of health services at Duke-National University of Singapore.

To see this "secondary effect" of a tax, though, the money generated from the tax would need to be spent on efforts to promote public health, Finkelstein told MyHealthNewsDaily.

The sweet lowdown
The researchers tracked the impact of a 20 percent and a 40 percent tax on sodas and other sweetened beverages on the calorie intake and weight of people at different income levels. They used information from a database of U.S. households that tracked their store-bought food and beverage purchases over the course of a year in 2006.

Each day, under a tax that raised prices 20 percent, most people would likely consume about seven fewer calories, on average, because they would replace soda or sweetened fruit drinks with other beverages. On average, people would shed about 0.7 pounds (0.3 kilograms), the researchers found.

A 40-percent tax would bring an annual weight loss of up to 1.3 pounds (0.6 kg) per person by causing a daily reduction of 12.5 calories, the researchers said.

"Although small, given the rising trend in obesity rates, especially among youth, any strategy that shows even modest weight loss should be considered," said study researcher Eric Finkelstein, associate professor of health services at Duke-National University of Singapore.

"Extending the tax to restaurants and vending machines would generate more tax revenue and perhaps greater weight losses," Finkelstein said.

The researchers analyzed purchases of sodas, fruit drinks, sport or energy drinks, fruit juice, and skim and whole milk. They then used statistical techniques to measure how changes in prices affected household buying habits.

Unlike previous studies, the new research included both weight losses resulting from fewer soda purchases and weight gains due to switching to other beverages, the researchers said. If people switch from Coke to Diet Coke or water, they'd lose weight, Finkelstein said. If they switch to other high-calorie drinks, such as fruit juices that do not have any sugar added or whole milk, then the effects of the tax are negated, he said.

The researchers also found that nearly all of the weight loss would come from people of middle-level income.

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A tax would have no effect on weight among consumers in the highest and lowest income groups, the researchers said, because high-income households would be unaffected by such a tax, and low-income households would likely avoid the tax's effects with cost-saving strategies such as purchasing generic versions, waiting for sales or buying in bulk, the study found.

What about the money?
A sales tax that raises the price of sweet drinks by 20 percent would generate about $1.5 billion per year in tax revenue in the United States, the study showed. A tax that raises prices by 40 percent would generate $2.5 billion per year, and cost the average household about $28.

Because poor households are more likely to buy generic brands, which are significantly cheaper, they would pay a smaller share of the total tax revenue, said study researcher Chen Zhen, a research economist at RTI International.

The study found that, for a 40 percent tax on sweetened drinks, those in the lowest 25 percent of household income would contribute roughly 20 percent of the tax revenue, while those in the highest income quartile would contribute 30 percent.

However, Finkelstein said, all groups could benefit from the tax if the revenue was used to fund obesity prevention efforts.

The findings are published today (Dec. 13) in the journal Archives of Internal Medicine.

Pass it on: Taxing soda may lead to a modest weight loss. Using the revenue for public health efforts could up the benefits.

Follow MyHealthNewsDaily Managing Editor Karen Rowan on Twitter @ karenjrowan. 

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