Forget the summer diet, September and October are all about putting on as much weight as possible for a warm, comfortable winter – or at least that's the case for the brown bears of Katmai National Park.
Every year, the park runs a fat bear tournament – now known as Fat Bear Week – where members of the public get to vote for which bear they think has what it takes to survive the winter.
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What is Fat Bear Week?
During Fat Bear Week, people from around the world cast their votes in a daily head-to-head, deciding which big bear deserves to be crowned as the plumpest.
Some of the largest brown bears on Earth make their home at Brooks River in Katmai National Park, Alaska. Brown bears get fat to survive and Fat Bear Week is an annual tournament celebrating their success in preparation for winter hibernation.
The National Park Service, Explore.org, and the Katmai Conservancy come together to celebrate these hefty bears in September and October, when they are at their fattest, by sharing before and after photos (as well as the bears' stories) for people to vote on.
When is Fat Bear Week?
Fat Bear Week 2026 takes place between 22–29 September.
How to vote in Fat Bear Week
You can vote in Fat Bear Week on the Fat Bear Week website.
How much do the bears weigh?
Adult males weigh on average 317–408kg in mid-summer before piling on the pounds by feasting on rich foods – usually salmon – to fatten up for their winter hibernation. During this time, they won’t eat or drink for several months and can lose a third of their bodyweight. They need to be as chunky as possible to survive the long winter. These girthy grizzlies do not disappoint, sometimes tipping the scales at over 544kg in the autumn.
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Who was the winner of Fat Bear Week 2025?
A male grizzly named 32 Chunk was crowned the winner of Fat Bear Week. After a battle with another bear left him with a broken jaw, Chunk had to learn how to fish without using his jaw fully. His determination and creativity to continue feeding in preparation for winter was clearly a hit with voters.
Why is Fat Bear Week so popular?
The popularity of Fat Bear Week has grown exponentially – largely thanks to the competition going viral on the internet (in a similar way that initiatives such as Fish Doorbell have). Fat Bear Week began in 2014 with 1,700 votes and has since grown into an international event, with over 1.2 million votes cast in 2024 from more than 100 countries. While we can't say for sure why it's so popular, the competition highlights the stories of each bear 'competing', documenting their triumphs and struggles as they prepare for a harsh winter. Many of the same bears return each year – sometimes with new cubs in tow – with voters following them over time.
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Top image: 2025's winner 32 Chunk. Credit: Candice Rush/Katmai National Park and Preserve
