Protein ain't the problem. You won't last long enough on low-fat, no-carb to worry about muscle loss... You'll simply either abandon it or starve yourself into a hospital bed or insane asylum, depending on the laws of your jurisdiction!
(Reason: low-fat diets' calories ALWAYS come from carbs - protein simply isn't found in sufficient amounts-ratios-concentrations anywhere to be the primary fuel for a human. Even so-called 'protein diets' are in fact hi-fat no-carb and have very little to do with the protein that the title implies.)