This ability to store fat as energy to use later is what kept our ancestors alive!
Up until a few hundred years ago, If you wanted to eat, you had to grow or kill something.
Cavemen knew little about agriculture and wild beasts were hard to kill with sticks and stones.
This meant that our ancestors went though prolonged periods of famine, but they were able to survive because humans developed the ability to store fat.
Our bodies use that fat as energy during times of caloric scarcity!!!