That's basically the Atkins diet (Keto) without enough nutrition. It'll function like a very short, very uncomfortable, malnourished crash diet.
You'll spend the first two weeks craving carbs and sugars like your life depends on it. It's awful. After that "break in" period, the cravings mostly go away.
But that's not all. So much as lick a piece of candy or chew on some bread, and you'll get a large dopamine rush followed by carb-craving mode again. If sheer willpower and deferred rewards are at all a problem for you, this might feel like one of the hardest things you've ever tried to do.
Edit: now that I remember, my grandma tried a "cottage cheese and grapefruit" fad/crash diet back in the 80's. Turns out that one has been doing the rounds for almost a century. IIRC, it doesn't work since it's easy to underestimate how insanely difficult this is to do.