I’ve done the very low carb/high fat diet before.
If you’re like most folks, you will lean out AND gain some muscle.
The principles of the diet are nothing new, as guys were doing it with great success in the 60’s.
Insofar as losing fat, the diet will provide the most optimum results if you follow it STRICTLY & CONSISTENTLY.
And, because testosterone is a lipid-soluble cholesterol derivative, adding healthy dietary fats will have a positive effect on your body’s natural sex hormone levels.
Increased serum test levels can only help in building muscle.
I never went the “zero” carb route, but I derive the vast majority of my calories from fats.
0-carb dieting often adversely effects neural function and/or energy levels, something I cannot afford right now.
Just be warned that, if you don’t keep your carbs low enough, it’s very easy to gain fat on this type of diet - thus, the necessity for strictness.
The degree will largely depend on you, as there are slight variances in how well different people can handle/metabolize carbs.