Drinking lots of soda is as one of Californians' worst health habits and contributes to the state's costly obesity problem. State Sen. Bill Monning is reviving the pat solution -- a soda tax that he says will reduce consumption, cut health care costs and raise hundreds of millions to help fight diabetes and other chronic diseases.

Singling out sodas above other high-calorie drinks and equally harmful junk foods isn't a bad idea for making a point, but it doesn't make for good legislation. To really make a difference in the obesity trend, lawmakers need to look more broadly at its causes and the public cost of unhealthy diets.

Monning cites a new study at UC San Francisco that predicts a soda tax could reduce California's health care costs by between $320 million and $620 million in 10 years. But rather than debating predictions, check out the actual experience of a state that has been in the vanguard of soda taxation: that model of progressivism, Arkansas.

Arkansas instituted a soda tax in 1992, as Gov. Bill Clinton's term was ending, for the same reasons Monning and some other Bay Area lawmakers have supported one. But 20 years later, the state's adult obesity rate had risen from 17 percent to 34. 5 percent.

In fact, Arkansas was the only state in 2013 to show an increase in its obesity rate, which is the third highest in the nation. It's on a par with neighboring states' that do not have a soda tax: Louisiana, 34.7 percent, and Mississippi, 34.6 percent.

Of course drinking more water and less soda is healthier for everyone, especially children. Anybody who doesn't know that just hasn't been paying attention. But sodas account for only 7 percent of Americans' caloric intake every day. Why should makers of other unhealthy foods skate?

Junk food is every bit as bad for people. The average Californian eats 30 pounds of french fries and 150 hamburgers a year, but no lawmaker is calling for a tax on fast food. Californians enjoy nearly 50 pints of ice cream a year, at 600 calories a pint, but Monning's tax would affect them only if they make root beer floats.

The Carmel Democrat is right about the problem California is facing. The Bay Area News Group's Jason Hoppin reported last week that according to the Centers for Disease Control, 2.5 million Californians had diabetes in 2010, a number that has doubled over the previous 15 years.

Dealing with obesity has to be part of the state's and the nation's strategies to bring down health care costs. But if California goes down the path of a sin tax on fattening foods and drinks, it should develop a thoughtful and comprehensive law, not follow in the pudgy footsteps of Arkansas.