TOKYO: It's wintertime and the king penguins at a zoo in northern Japan are putting on weight. But the keepers there have a solution: exercise.

Authorities at Asahiyama Zoo are taking the penguins on 450-metre walks on the snowy grounds twice a day, said zoo spokesman Tetsuo Yamazaki.

"Just like humans ... the fat accumulates during the winter months, and the blood-sugar level rises," Yamazaki explained from the zoo, 912 kilometres northwest of Tokyo.

The zoo's 15 king penguins are not exactly obese. Penguin winter weight varies from 15 kilograms to 18 kilograms, said zoo official Kazunobu Maru. So far, only one of the flock is 18 kilometres, he said.

The reason for weight gain is natural, zoo officials say.

"In order to withstand the cold, the penguins have a habit of standing very still during winter months," Yamazaki said, while in the summer they can walk around and swim as much as they want.

To fend off obesity, the zoo instituted the winter exercise programme in 2003.

The penguins have tender webbed feet and can only walk significant distances on snow, so the programme can only take place during the colder months.

The zoo, on the northern island of Hokkaido, takes the penguins on strolls from December until April.

Source: China Daily