In African ponds lives a fish that manages to grow old within a single summer. Scientists noticed that if you feed it every other day, it lives longer. But the most interesting part is how fasting affects muscles. In females, it restores the fast-twitch muscle fibers needed for sudden movements. In males, fat and sugar processing improves.
This is like renovating a house: females fix the wiring, while males fix the heating. That's why the same diet can't help everyone equally. Doctors should consider a patient's sex when they recommend fasting to preserve strength in old age.
The killifish Nothobranchius furzeri lives in ephemeral pools in Mozambique and Zimbabwe that dry up within a few months. Its eggs can survive complete desiccation in diapause for a year or more. In the laboratory the fish live 4-6 months, making them the shortest-lived vertebrates bred in captivity.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.