In the government's effort to fight obesity, don't just put out nutrition guidelines and broadcast public service announcements. Instead, let's spend more money.

That's the logic of a proposal from two Canadian academics, detailed by a Friedrich Hayek-quoting Matt Ridley Monday in the Wall Street Journal, for the government to give Americans “‘healthy living vouchers’ that could be redeemed from different (certified) places — gyms, diet classes, vegetable sellers and more."

"Education vouchers," Ridley continues, referencing the academics’ work, "are generally disliked by rich whites as being bad for poor blacks — and generally liked by poor blacks. A bottom-up solution empowers people better than top-down government fiat."

But the analogy to education vouchers is inappropriate. Everyone has to "buy" education, or the government will for you. No one has to buy a gym membership. Government already puts mountains of cash into education, making vouchers an attractive reallocation of those resources. Not so with government sponsorship of healthy habits.

This voucher proposal exposes a perverse logic so often at work in Washington policy circles. Vouchers — a form of government spending — might encourage rational behavior, and since participating taxpayers see the direct benefit they are getting from the program, many like it. But vouchers cost money and rely on consumers to opt in — to buy and use a gym membership or vegetables while eliminating bad habits. So they don't encourage as many people to change behavior as other consumer-focused policies, but they do transfer money to people who would have cultivated healthy habits, anyway. Which is nice, but not efficient public policy.  

Before handing out vouchers, we should simply tax unhealthy food. Doing so costs the government little to administer — certainly much less than a complicated system to decide who can cash a voucher and for what purpose, to combat voucher fraud, and so forth. It need not cost consumers too much up front — as Washington's plastic bag tax illustrates, the psychological power of rising prices can be large relative to the expense. And instead of costing every taxpayer money, it raises cash from those whose unhealthy eating habits result in high medical bills, the cost of which will be passed on to the rest of us eventually.

Unlike more government spending, new taxes are exceptionally difficult to pass. But Congress can start affecting the price of bad-for-you food by rescinding massive subsidies for sugar, corn and other agricultural products that contribute to obesity, which also saves money instead of spending it.

Ridley would probably point out that healthy-living vouchers cover much more than diet — they can pay for exercise classes or other expert help, allowing people to design a weight-loss program that works best for them. True, but this overcomplicates the obvious: Get people to eat less unhealthy food, and they won't be as fat.