The Wall Street Journal reports today on a voluntary commitment made by the giant soda manufacturers to produce lower-calories drinks, smaller size cans, etc. The goal is to try and address the fact that about one-third of American adults and one in five kids refuse to control their calorie intake and, thus, are obese. It will clearly be very costly.

Under the voluntary agreement announced Tuesday, the companies said they would market and distribute their drinks in a way that should help steer consumers to smaller portions and zero- or low-calorie drinks. They also have committed to providing calorie counts on more than 3 million vending machines, self-serve fountain dispensers and retail coolers in stores, restaurants and other points of sale.

But in predictable fashion, that isn’t enough for a well known group of liberals.

The Center for Science in the Public Interest, a longtime soda industry critic, called the move “welcome news” but said the goal could be achieved much faster with taxes on soda and warning labels. “We need much bigger and faster reductions to adequately protect the public’s health,” the group said.

Two lessons can be learned here. First, liberals prefer using the government stick rather than looking to private players to respond voluntarily. Second, liberals understand quite well that when you raise the tax on something, you will get less of it.

What’s more, as is typically the case with stories about the obesity problem, there’s no mention of the fact that all of this can be addressed if people would (1) stop gorging and (2) take a walk around the neighborhood.