If a pharmaceutical company offered me or any other doctor money to prescribe one of its drugs, we would be expected to reject it. Despite criticism from the Inquirer Editorial Board and City Council, Mayor Nutter's decision to reject an antiobesity program funded by the Children's Hospital of Philadelphia with money from the soda lobby is just as sound. Such industry support is designed to dissuade city officials from enacting a soda tax.

Last year, when Nutter first proposed a soda tax, it was rejected by Council. Many have apparently forgotten that a soda industry donation for antiobesity programs was offered soon after Council's rejection of the tax. An Inquirer editorial at the time said, "Instead of pay to play, it's pay to go away."

That's as true now as it was then: These contributions are driven by politics and public relations. Where was the soda industry before the mayor proposed a tax?

There has been growing recognition over the last decade of the pharmaceutical industry's powerful influence among physicians. That influence arose partly from the medical profession's substantial dependence on the industry for support of crucial programs such as continuing medical education. Education is a worthy goal, but it is the drug industry's funding itself that raises concerns, not the use of the funding. Such support makes it harder for doctors to disentangle themselves from an industry that is trying to influence the prescriptions they write.

There are lessons here for public health. Accepting support from an industry can have an impact that goes beyond the stated purpose of the funding. If the city's Department of Public Health accepts soda industry money, making public programs dependent on that money, you can bet those programs will become bargaining chips in future political fights. Can we really believe that such programs wouldn't be vulnerable if the city passed a soda tax?

If the tobacco industry offered to voluntarily fund antismoking programs, we would all recognize the problem with the arrangement. We may not regard soda companies the same way we do tobacco companies, but soda is a major public-health problem, and depending on its makers to solve it would be ill-advised.

I have many obese patients. Too many of them were already obese on their 18th birthdays. And many will need gastric bypass surgery by age 30. Otherwise, they face early deaths from diseases such as diabetes.

The epidemic of obesity starts in childhood. Parents have an important role in preventing it. But government can be a strong partner, and a soda tax is one way it can help families make healthier decisions. The mayor is right to take a stand on soda, and we should applaud him for refusing to let the soda lobby to buy off the city government.

David Grande is a physician and a senior fellow at the Leonard Davis Institute of Health Economics at the University of Pennsylvania. He can be reached at dgrande@wharton.upenn.edu.