“The most important finding of our study is that a tax of 25 percent or more on (high-calorie) foods makes nearly everyone buy fewer calories,” Giesen told Reuters Health in an email.

For people who are weight- and diet-conscious, calorie information might trump price, according to Giesen. “However, if one wants to help people in general to prevent caloric overconsumption,” the researcher said, “then our results indicate that imposing a high tax on (high-calorie) food items is much more efficacious.”

A researcher not involved in the study noted that it had a number of limitations, including a small sample size.

Still, it jibes with larger experiments suggesting that food taxes might work, said Dr. Barry Popkin, a professor of nutrition at the University of North Carolina, Chapel Hill, who has studied the potential effects of junk food taxes on people’s food choices.

In an email, he pointed to a recent study by Harvard researchers in which they added a 35-percent tax to sugary sodas sold in the cafeteria at Brigham & Women’s Hospital in Boston. They found that sales of sugar-sweetened sodas dropped by 26 percent, and that people tended to replace those drinks with diet soda or coffee.

In contrast, an educational campaign - where signs were posted recommending that people cut back on sugary soft drinks - failed to make a dent in sales.

According to Giesen, studies are still needed to see whether smaller tax increases - something closer to 10 percent, which would be more politically viable - influence people’s buying habits.

Industry trade groups like the American Beverage Association and anti-tax activists like Americans Against Food Taxes (which has industry backing) argue that there is no evidence that junk food taxes will fight the U.S. obesity problem. They also assert that such taxes will only unduly burden low-income families.

SOURCE:  American Journal of Clinical Nutrition, online January 26, 2011.