CHAPEL HILL, N.C. — Raising the price of soda or away-from-home pizza may be effective in steering consumers toward a more healthful diet and help reduce long-term weight gain, according to a study published in the March issue of the Archives of Internal Medicine.

The 20-year study (1985 to 2006) led by researchers from the University of North Carolina at Chapel Hill looked at 12,123 respondent days from 5,115 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study. Research included examining associations between food price, dietary intake, overall energy intake, weight and homeostatic model assessment insulin resistance.

What the researchers found is that while the real price of soda and pizza decreased over the 20-year period, a 10% increase in the price of soda and pizza equated to a 7% and 12% decline, respectively, in daily energy intake, as well as to lower body weight.

“Price manipulations on unhealthful foods and beverages have been proposed as a potential mechanism for improving the diet and health outcomes of Americans,” the researchers wrote. “While some argue that there is little evidence such a tax would improve health or have a positive impact on obesity rates, to our knowledge, no research has examined the direct and indirect total effects of such taxes on energy intake and subsequent changes in weight and other metabolic outcomes.”

The researchers estimated that an 18% tax on sodas and away-from-home foods — the level unsuccessfully proposed by the state of New York — would result in a decline of about 56 calories per person, per day. This would amount to approximate weight loss of 5 lbs per person per year, the researchers noted.

“Our findings suggest that national, state, or local policies to alter the price of less healthful foods and beverages may be one possible mechanism for steering U.S. adults toward a more healthful diet,” the researchers wrote. “While such policies will not solve the obesity epidemic in its entirety and may face considerable opposition from food manufacturers and sellers, they could prove an important strategy to address overconsumption, help reduce energy intake, and potentially aid in weight loss and reduced rates of diabetes among U.S. adults.”