jshevach's Journal, 26 January 2014

Not sure how you think exercise causes loss of muscle. The only time that might be is if you do hours of cardio and don't get the proper nutrition needed. Protein and exercise help build muscle. Your body relies on fat, carbs and protein as its three sources of fuel for energy, albeit in different ratios depending on your activity intensity and duration. During low-intensity cardiovascular exercise such as walking at a moderate pace, your body uses more fat as fuel. If you pump up the intensity of your workout and break into a run, your body uses a higher percentage of carbohydrates as fuel as you activate more “fast-twitch” muscle fibers and levels of the hormone epinephrine rise. With protein, the body doesn’t usually turn to protein as a fuel source except under unusual circumstances. You should always remember that when exercising your body will always prefer to burn Carbohydrates (both stored and from foods you have eaten) first, then Fats (from foods you have eaten and from your stored fat cells) and as only a last resort Proteins (amino acids from muscle tissue). Protein before a workout and some carbs to help replace afterward might work. But the fact that you have so little to lose and are already at a low weight might be part of the reason why you are only losing a small amount at a time. If you weigh in on a scale with fat percentages, they are not always that accurate. They can change from hour to hour. Try different things and see what works for you. Good luck!