Children in Fukushima are getting fatter as outdoor activities have been cut in the area due to radiation fears after last year's nuclear disaster, a Japanese government report said Tuesday.

The education ministry said it had surveyed the heights and weights of about 700,000 children, aged between five and 17, at schools and kindergartens across the country this year.

It compared the number of obese children, defined as weighing at least 20 percent more than the average for their age and height, among the 47 prefectures.

Fukushima registered the highest rates in seven of the 13 age groups, the ministry said. In 2010, the prefecture on the north of the main island Honshu topped the table only in the 10th year of school.

"The amount of exercise has declined in Fukushima, mainly among elementary school pupils, as outdoor activities in some locations have been restricted after the Fukushima Daiichi nuclear plant accident," a ministry official told a news conference.

In Fukushima, 449 -- or 56 percent of public schools -- curbed outdoor activities during school time as of June last year due to radiation concerns, Kyodo news agency said.

Such restrictions remained in place at 71 elementary and junior high schools as of September this year, Kyodo said.

In the accident of March last year, an earthquake-triggered tsunami smashed into the Fukushima nuclear plant, sparking meltdowns and explosions.