A New Weight-Loss Plan: Getting Paid to Shed Pounds

There are plenty of reasons for Welmoed Sisson to lose weight. She'd feel better, be healthier and fit into that skirt she wore 20 years ago before she became obese. She knows all this, and yet there may be only one incentive powerful enough to get the 49-year-old resident of Gaithersburg, Md., to pass on the delicious steaks her husband cooks. The motivator? Cold, hard cash.

Financial incentives are the latest wellness craze, inspiring at least some of the nearly two-thirds of Americans who are overweight or obese to try to ditch their potato chips. A few...