NEW YORK (Reuters Health) - People are generally more likely to pass on high-calorie food when there is a tax on it -- though it might not matter to everyone, a small study suggests.
In a computer-based experiment with 178 U.S. college students, researchers found that the students generally "bought" fewer lunchtime calories when sugary, high-fat fare came with a tax of 25 percent or more.
The exception was when calorie-conscious eaters were given calorie information on their lunch options; the tax did not seem to sway their decisions.
Junk food taxes and greater openness with calorie information have both been advocated as ways to help consumers limit their calories -- and, the hope is, keep their weight in the healthy range.
In the U.S., proponents of taxes on soda and junk food argue that it would not only discourage people from buying them, but could also help offset the estimated $147 billion cost of treating obesity-related ills.
Supporters also point to research suggesting that cigarette taxes have helped curb tobacco use.
Policies to require restaurants and other vendors to be frank with calorie information have made greater gains. In 2008, New York City became the first U.S. city to mandate that fast-food and coffee chains put calorie information on their menus. And in 2010, the federal healthcare reform law set national labeling requirements for certain restaurants and vending machines.
But just how effective such measures have been, or could be, is controversial.
A study reported on Tuesday, for example, found that New York City's law has so far done little to change children and teenagers' eating habits at fast-food restaurants.
The current study, reported in the American Journal of Clinical Nutrition, suggests that the effectiveness of junk food taxes might partly depend on whether calorie information is given or not -- and the customer's own calorie-consciousness.
For the study, researchers led by Dr. Janneke Giesen of Maastricht University in the Netherlands had 178 U.S. college students choose a hypothetical lunch from a computer menu on three separate occasions.
Each time, the prices for high-calorie items -- like bacon cheeseburgers, brownies and chips -- were increased, first by 25 percent and then 50 percent.
About half of the students were given calorie information at all lunches, while the rest were not.
Overall, Giesen's team found, students tended to order fewer calories when a junk food tax was in place. They curbed their average calorie intake by about 100 to 300 calories depending on the tax in place.
The only students who did not respond to the price increases were those who were already watching their diets and were given calorie information. They ate fewer calories than their peers without any food tax, and showed little change in their eating when taxes were added.
"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: bit.ly/gsz9pw American Journal of Clinical Nutrition, online January 26, 2011.