Drinking soda is linked to obesity - but a new study claims not in ways that should increase taxes on it.

A study by Northwestern University looked on whether food taxes decrease the risk of heart disease and other obesity related problems and found that it didn't in ways that policymakers have said.

Ketan Patel, a doctoral student in economics says that "It's possible that a tax on soda would help people who are normal weight or overweight from becoming obese, for those who are already obese, a soda tax doesn't look like it would be effective. It turns out that obese consumers have a strong preference for diet soda."

A proposal by the Illinois Senate would raise a penny an ounce on the state but would not apply to diet drinks, whilst hoping to decrease the cost of obesity-related health problems about $150 million.

"The tax would have a positive public health impact by reducing soda beverage consumption and obesity," said an economics professor, Frank J. Chaloupka.

"There's very little funding for those sorts of efforts, so additional revenues could help support efforts that would add to the effect of the tax and reduce obesity." he added.

By taxing a penny an ounce, Frank hopes that 45,000 fewer children will suffer obese diseases, and that 140,000 or so fewer obese adults would suffer the disease.

His research also shows that the amount of expenditure on obese people would fall by $150 million.

His study can be found here.