People following a 5-2 diet would eat lean protein and non-starchy vegetables two days a week. Heather Rousseau/NPR hide caption

itoggle caption Heather Rousseau/NPR

A player avatar runs on a treadmill in the virtual world of Second Life. Researchers used the online game to see if it could help people maintain weight loss habits in the real world. Courtesy of Univeristy of Kansas Medical Center hide caption

itoggle caption Courtesy of Univeristy of Kansas Medical Center

Drinking diet soda and other low-calorie drinks may help you manage weight, but experts say plain old H2O is still the best way to go. Justin Sullivan/Getty Images hide caption

itoggle caption Justin Sullivan/Getty Images

Eating low-glycemic foods, or foods that take longer to digest, may help you feel fuller for a longer period of time. Robyn Mackenzie/iStockphoto.com hide caption

itoggle caption Robyn Mackenzie/iStockphoto.com

It doesn't take a transcontinental flight to end up out of sync with your body clock. It might just be that you stay up too late. iStockphoto.com hide caption

itoggle caption iStockphoto.com

The FDA hasn't approved a new weight-loss drug since 1999. In the meantime, Americans' waistlines have continued to grow. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP

Jenny Craig brand ambassador and singer Mariah Carey (left) poses with Dana Fiser, CEO of Jenny Craig, at a press conference in New York City in November. Cindy Ord/Getty Images hide caption

itoggle caption Cindy Ord/Getty Images