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Lipids store long term energy. That's why bears build up a lot of lipids (fat) before they go into hibernation!
Explanation
Lipids provide insulation. That's why seals will have lots of fat (blubber) under their skin to keep them warm in cold ocean waters.
Carbohydrates provide short term energy. Think about how eating lots of sugar makes you really hyper or how athletes will "carbo-load" before a big game or meet!
Protein does NOT provide energy!! Don't be fooled! It helps build muscles and makes helps with cell processes.