Why do cetaceans need a thick layer of fat?

Fats have many important functions and properties. One of these properties is low thermal conductivity. Since whales are mammals, they are warm-blooded. To retain this heat in low ocean temperatures, they have to deposit a thick layer of fat (up to 1m). These fat reserves also allow whales to go without food for a long time at the time of migrations. Energy during this period is obtained due to the breakdown of accumulated fat (1gr = 38.9 KJ).