How can you lose weight without losing muscle?

Do long sprees of Cardiovascular exercise (I prefer running in place + jumping jacks to music) 5 days a week. A minimum of 20 minutes a day. Take a 5 minute break for water and some fresh air for every 10 minutes of consecutive exercise. In terms of food, don't kill yourself with worry; your body needs "good" fats, carbohydrates, and proteins, and calories to recover after wards. I suggest eating a healthy, semi-high calorie breakfast (2 eggs on 100% wheat toast + bowl of wholesome cereal) and leave the rest of your daily meals to reasonable snacking here and there. The reason why is that your muscles use up all of what you eat to recover in a short amount of time. If there is constant healthy sources of fuel (fruits, veggies, chicken, fish, whole grain snacks, milk, etc) your muscles have the supplies they need to replenish, grow and function side by side with your metabolism.