Kodiak bears are heavy eaters, but during the spring and before the spawning salmon season begins they eat about 50 pounds of food per day. This low intake, compared to their summer dietary intake, is due to many factors, some of, which include the climate, abundance of food and the availability of food that contains a high amount of fat and nutrients.

Most of the food that a Kodiak bear eats is plant material, which seems to label the Kodiak as a herbivore, but the remaining dietary intake of this animal comes directly from the fish, carrion and occasional game animal that they eat. The Kodiak bear's vegetation intake usually comes from wild relatives of the carrot, lettuce, berries and various types of grasses.

When the spawning salmon season begins in Alaska, Kodiak bears digest approximately 50% more food than it ate during the spring. This increase of food intake is due to the abundance of salmon and the nutritional value that it possesses. Depending on the amount of salmon available, the Kodiak bear usually strips away all of the fish except for the stomach, liver and intestines, which it leaves for the scavengers that live in the same environment.

All bears use different techniques and strategies to catch fish, the most common of which is the bear jumping headlong into the river and then proceeding to claw their paws in the river. Other techniques include the Kodiak waiting along an area where the fish jump high enough for the bear to grab it and the submarine technique.

This submarine technique involves the bear submerging in the water, with only its ears above the water. The Kodiak will then push itself underwater, while wading up the river. While the bear performs all of these measures it also will simultaneously look for a fish, and if it finds one it will simply swim at the fish with its jaws open.

Kodiak bears will also scrounge through beach drift, which includes seaweed, mollusks, crabs and washed-up marine mammals, such as a whale and sea lion. They also prey on young and sick moose calves, deer, elk and caribou. It rarely chases and hunts a healthy game animal because the game animal will out run it in both short and long distances. When a Kodiak kills a large animal which is too large to be consumed all at once, they will hide it from other animals in a secluded area so they can return to it in the near future to finish consuming the animal.

More than half of the yearly diet of Kodiak bears consists of berries and grasses. Due to low concentration of food value in single plants, Kodiak bears have to eat a lot of plant material to gain any weight.

The claws of a Kodiak bear, which is designed for digging, are used to capture yet another prey for the Kodiak bear, the marmot. The Kodiak bear captures these underground animals by digging through areas that the bear can sense as belonging to the marmot.

The Kodiak bears' weight keeps it from being fast enough to catch some healthy game animals, which can run over 35 mph over short distances. Kodiak bears are also not stealthy enough to sneak up behind a game animal and kill it. There are a few scenarios in which it is possible for the Kodiak to attempt to catch a healthy game animal. The most common scenario would be at river crossings, at which the game animals do not pay attention to their surroundings.