@Alvin – That’s a great question. From my own experience with my training clients, I never had one client lose an ounce of muscle while losing fat (well actually one who tried a very low carb diet when he was already lean). This is because they did intense strength training, did not go too low on the calorie deficit, and ate sufficient protein (roughly per pound of body weight). I think if you follow these 3 guidelines, you can keep the vast majority of your muscle mass. As you start getting around 10-12% body fat, it’s very possible that you lose a little muscle mass. So let’s say a bodybuilder looking to get shredded for competition may lose 3-5lb of muscle as he strips his body of all the fat he can.