Last week, I happened to read about Kleiber’s law while browsing through literature on natural evolution. The implications are really fascinating. It establishes a relationship between mass and metabolism as:

$$metabolism = mass^{\frac{3}{4}}$$

Metabolism is ultimately linked to the number of heartbeats since the heart regulates the supply of oxygen. Therefore, $$\mid heartbeat \mid \propto mass$$. Curiously, the number of heartbeats per lifetime tends to be constant. This means that bigger/heavier animals tend to have slower metabolism with lower heart rate compared to, say, flies, with faster metabolism.

Ironically, if we have fixed number of heartbeats, wouldn’t running/exercising make us die faster? I suppose, the long term benefits outweigh shot term loss.