Desperate to curb the nation's obesity problem, the U.S. government has put a lot of effort into figuring out how to make kids eat their fruits and veggies. The latest approach, as mandated by the 2010 Healthy and Hunger-free Kids Act: Require that all $31.6 million federally-subsidized school lunches include at least one of them, whether the kid chooses it or not. Right now, that's costing an extra $5.4 million a day.

The problem? Although more kids eat things like apples and carrots when they're provided with them by default, about 70 percent still get thrown away.

But there appears to be a better way. According to a couple new studies from Cornell and Brigham Young University, offering rewards for actually eating them results in much higher consumption and much lower waste -- it costs $1.72 to get a kid to eat an apple under the current default system, and would cost about 35 cents if kids were offered a small reward for doing so. That shakes out to $1.1 million a day, instead of $5.4 million.

To figure this out, the researchers tested a control population of elementary schools in Utah in which kids were provided with servings of fruits and vegetables by default against a set of schools where kids were compensated in a variety of different ways for taking them voluntarily. The results were fairly dramatic: In the default scenario, the percentage of kids eating one serving per day increased 10 points, but four times as much produce got wasted. When kids were rewarded with a nickle or a quarter or a raffle ticket for actually eating the stuff, consumption rose 80 percent -- and waste decreased by 33 percent.

The effect comports with other kinds of research about kids' motivations: Financial incentives work when getting kids to do concrete tasks like homework, but not for outcomes, like getting good grades. If that logic holds, it probably also wouldn't work to pay kids for losing weight -- but getting them to eat more healthfully might at least instill better habits, and save money in the process.