Alaskan Brown Bear. Alaskan brown bears are the largest brown bears and require a very high caloric intake of food. Brown bears in Alaska can eat 80 to 90 pounds of food per day in the summer and fall, gaining around three to six pounds of fat each day, in order to store fat for the winter. Alaskan brown bears are opportunistic eaters and will eat almost anything. Their diet consists of berries, flowers, grasses, herbs, and roots. They get their protein from beavers, deer, caribou, salmon, carcasses, and other small mammals.