We've known for over a century that mice and rats live longer when they are fed less, but a new study reveals the secret might be an imbalance between energy consumed and burned, rather than a lack of energy or protein.

A longer experiment followed mice from 12 weeks old for the rest of their lives. Those kept at 22 °C lived about 20 percent longer than those fed the same but kept at 27 °C. Mice that lived in cooler cages were also healthier as they aged compared to the warmer mice, whose balance, coordination, and neurological function declined faster.