Taxing sugary foods and drinks likely would impose increased costs on consumers without significantly altering behavior, researchers argued this week.

Donald Marron, director of economic policy initiatives at the Urban Institute, said that unlike the tight link between cigarette smoking and worsened health, the effects of eating and drinking habits are more difficult to pinpoint.

“For things like smoking, the reality that you’re making some people’s lives sincerely more difficult by raising the price of the habit of smoking is more than justified by the fact that it is insanely bad for you,” Marron said during an Urban Institute panel discussion Tuesday. “When you get to nutrition, it’s a little less clear.”

Policymakers concerned about obesity hitting an all-time high in the United States are debating whether to tax sugary drinks and junk food to motivate Americans to select healthier options.

Lawmakers across the U.S. for years have tried and failed to levy taxes on sugary foods and beverages after consumer pushback and criticisms of government overstepping.

This year, Berkeley, Calif., became the first city to implement a tax on sugary beverages such as sodas and energy drinks.

Though it is too soon to fully examine how the tax will affect consumption levels in Berkeley, researchers said similar policies in Mexico, Denmark and France offered insight.

Marron said metabolisms, overall health and lifestyles differ from person to person, causing sugar consumption, for example, to affect individuals at varying levels.

Maeve Gearing, a research associate at the Urban Institute, said nutritional science isn’t conclusive enough for sugar and other nutrients to be considered in the same league as cigarettes and alcohol, “where there is clear and demonstrated addictive aspects as well as very clear ties to particular ills.”

“Without that justification, it does not make sense for the government to step in,” she said.

Marron and Gearing co-authored a report published Monday that investigated whether the government should move to tax unhealthy foods and drinks. 

Gearing said their research found that the effects of such a tax seems to be “muted,” but evidence shows declines in consumption of taxed products.

What is less clear, she continued, is whether consumers substitute one unhealthy product for another. Consumers may buy less soda because of the higher cost, for example, but it’s difficult to track whether individuals replace soda with water or energy drinks.

Gearing said a 10-percent sugar tax is estimated to decrease obesity by only one to three percentage points.

She said the decline, even if slight, does matter. But, she added, given the current obesity rate—more than one-third of Americans are obese—such a slight drop is not going to “get rid of the crisis.”

“We’d like it if people change behavior without having a tax,” Gearing said, adding:

To the extent that we can have people come together and encourage healthier behavior, that’s really the way that we should go in having people think about their diets in a different way, rather than by strictly restricting their ability to make that choice at all.