Animals that hibernate eat a lot before going for winter sleep. Why?

Hibernation:

• Hibernation is a state in which the metabolic activity and the body temperature of certain mammals are lowered as an adaptation to adverse winter conditions.
• Before going into a winter sleep the animals eat a lot of food to store the food for survival in their body in the form of fat because they have to hibernate for a long time means they will not eat anything during winter sleep.
• The productivity and temperature of such animal bodies reduce during winter sleep.