u/Adventurous-Idea-518

I read a book when I was a kid (so likely in the early 2000's) where at the end of WW2 Germany retreats to this impenetrable bunker. The protagonist was a scientist of some kind who discovered a way into the bunker and went undercover. He took the identity of someone in his field and tried to find a way to disable the bunkers defenses.

I remember him having an assigned amount of food and drink. He weighed a few lbs more than the identity he stole so he was forced (by a computer system maybe) to eat less to lower his weight to a more desirable number.

(Very 1984 vibes obviously)