To be in ketosis is not necessarily eating tons of fat but to keep insulin level down all the time. This forces the use of adipose mass to fuel yourself. The protein requirement must match your physical activity: eat too much and gluconeogenesis will produce glucose out of excess proteins, eat too little and your muscle will be used for glucose (brain needs). But that's the beauty of ketosis, you shouldn't have to eat up your muscle mass. You regulate your fat loss by how much fat you eat and your physical activity (slow pace is mostly fat-burning).