A brown bear known as 89 Backpack has won the annual Fat Bear Week competition, after what the US National Parks Service described as a "battle of size, skill, snack acquisition, and strategic loafing".

Backpack's wideness narrowly defeated a bear known only as 910, earning 103,344 votes to 910's 98,253 in the final round of the competition, which is run by the Katmai National Park in Alaska.

The National Parks Service thanked the 16 bears who "involuntarily participated" in the competition, now in its thirteenth year.

Backpack, who was described by one supporter as having both the "chonk and the badonk", will shortly enter hibernation, which can last up to six months.

His mother Holly was the 2019 Fat Bear Week winner. Backpack's name derives not from what another supporter described as the "light bulb shape" of his body, but his habit, as a cub, of climbing onto Holly's back when she waded through the park's salmon-filled Brooks River.

Another supporter described him as being a "big fuzzy boy".

But Backpack was not without his detractors. One person said she felt that Bear 910, a female who raised both her biological cub and an adopted niece, was a "larger bear all around. Backpack just has a bigger booty".

"I just feel like 910 really put in the work this year," another 910 fan wrote on the park's Facebook page, while a voter commented, "She round, she thick my girl 910 got my vote."