Confused by the structure used in a sentence I read.

[LesChaosEmeralds]

Hello. I was wondering if somebody could translate a sentence I read in a book today. The sentence is: “Vous vous apercevez qu’un homme qui a passé ne serait-ce qu’une semaine au régime du pain et de la margarine n’est plus un homme mais uniquement un ventre, avec autour quelques organes annexes “.
Thank you very much for your help.

[...hat...]

"You realize that a man who has spent just a week eating bread and margarine is no longer a man, but just a belly, with some of his organs."

[Fayke]

You realize that a man who has spent a mere week on a bread and margarine diet is no longer a man, but only a stomach, with some accessory organs around attached to it.