[logfromblammo]

In the degenerate case where you restrict your diet to zero calories over an extended period of time, your metabolism will permanently down-regulate to burn zero calories.

I think most people agree that should be avoided.

[samolang]

That is not true. What do you think the purpose of fat is? As long as you have fat supplies, your body will use those fat supplies. Example: http://www.abc.net.au/science/articles/2012/07/24/3549931.ht...

[logfromblammo]

It was a tongue-in-cheek reference to death from complete starvation. It is true in the sense that the basal metabolic rate of a dead body is zero kilocalories per hour.