A month is fine. A healthy person takes about 3 weeks to die with no food. A person with ample fat reserves would (or at least should) last longer.

Angus' feat was done with close supervision and (as far as anyone can cite) only once. I'm skeptical, as I said, and there's nothing radical about the idea of fat reclamation falling short of subsistence. I'd be curious to see someone replicate it.