After being fingered as a key cause of the rising rate of US childhood obesity, video games got a reprieve Tuesday as a new study showed they can be used to encourage kids to eat healthier foods.

The study, conducted in the United States, where nearly one in five six- to 19-year-olds is obese, found that children who played certain "serious" video games -- not the blockbuster blood-and-guts ones like "Black Ops" -- increased the amount of fruit and vegetables they ate per day by around one serving.

That is a useful step towards fighting childhood flab because "increased fruit and vegetable intakes have been associated with decreased risk of obesity," says the study published in the American Journal of Preventive Medicine.

Baylor College of Medicine professor Tom Baranowski, who led the study, said the video games "Escape from Diab" and "Nanoswarm," which were designed to change diet and physical activity behaviors to reduce the risk of becoming obese and diabetic, "motivated players to substantially improve diet behaviors.

"Diab and Nanoswarm were designed as epic video game adventures, comparable to commercial quality video games. These games incorporate a broad diversity of behavior change procedures woven in and around engrossing stories," he said.

Playing both games several times "had a meaningful effect on dietary fruit and vegetable intake," the study found.

But while that was good news, the bad news was that the children did not get more exercise, and, even with their increased intake of healthy foods, they still failed to eat the doctor-recommended minimum daily amount of fruit and vegetables.

Health professionals recommend that children eat five servings a day of fruit or vegetables and get an hour of moderate to vigorous exercise.

"Serious video games hold promise, but their effectiveness and mechanisms of change among youth need to be more thoroughly investigated," said Baranowski.

The childhood obesity rate in the United States has tripled in 30 years, with experts blaming the rise on everything from a poor diet based on processed foods to kids spending too much time in front of the television or playing computer games when they could be outside exercising.

Obese children are more likely than their normal-weight counterparts to grow up to be obese adults, to suffer from a number of obesity-related conditions including diabetes, cadiovascular disease and fatty liver disease, and to die prematurely of any cause, various studies have found.