Sure, it’s possible for you to lose muscle from doing too much cardio, but it’s highly unlikely. Shying away from cardio completely because you think you’ll lose muscle is a huge mistake. Only excessive amounts of cardio would cause you to lose muscle because over-training tips the scale towards the catabolic side. It’s difficult to generalize and pinpoint one specific amount as too much, but I think it’s safe to assume that just about anyone could do up to 45 -60 minutes of cardio a day, 6 to 7 days a week without losing any muscle – as long as the proper nutritional support is provided.
Losing muscle has more to do with inadequate diet than with excessive aerobics. If you suspect you are losing muscle there are four likely causes:
1. You are not eating enough calories to support muscle growth- This is the most common cause of muscle loss. When your calories are too low, your body goes into “starvation mode.” Your metabolism slows down and your body actually burns muscle tissue to conserve energy. Muscle is metabolically active tissue, requiring a great deal of caloric energy just to maintain it. That’s why your body will shed muscle if it thinks you are starving.
2. You are not training with weights- It is a common misconception that if you want to lose weight, you should start with cardio only and add the weights later – another big mistake! It is the weight training that keeps you from losing muscle while you are dieting.
You are much more likely to lose muscle from not eating enough than you are from doing too much cardio. All too often, people are afraid to eat a lot and do a lot of cardio at the same time. It doesn’t seem to make sense. Logically, it seems like the two would cancel each other out – but the opposite is true. Many people believe they must “starve” the fat by drastically lowering calories. Unfortunately, this approach can cause you to lose muscle along with the fat. The only way to maintain your lean mass while losing fat is to feed the muscles with plenty of nutritious calories and at the same time,burn the fat off with cardio.
3. You are not eating enough protein- Protein is the only nutrient that is actually used to build muscle. To stay anabolic you must eat five to six protein containing meals. Each meal should be spaced out approximately three hours apart. Research has proven that if you are physically active, you need a minimum of .8 grams to 1.4 grams of protein per kilogram of bodyweight.
4. Your carbohydrates are too low- Low carb diets are often used for fat loss, but it is a mistake to cut your carbs too drastically. Carbohydrates are protein-sparing , so even if you are eating large amounts of protein, you can still lose muscle if you your carbs are too low.