I think the person you're replying to is talking about the difference between maintaining a low-carb diet, and ketosis, which requires you to maintain a low-car

I think the person you're replying to is talking about the difference between maintaining a low-carb diet, and ketosis, which requires you to maintain a low-carb diet but specifically IIRC forces your body to break down fats instead of sugars in your body for energy.