Q: Is it really possible to lose muscle mass and density??? If so, how?... I haven't worked out or done anything for a month, since I've been busy.

A: Yes, it's very much possible to lose muscle mass. In fact it's a completely normal physiological process. Muscle loss can happen due to any number of illnesses as well as due to natural aging, but the two factors that cause muscle loss that you can easily control are diet and exercise.

The biggest reason muscle loss happens in normal healthy people is due to caloric deficit. Basically this means the person is burning more calories than she is eating. At this point her body needs to tap its energy reserves to make the up the deficit in calories. The body's primary energy reserve is of course, body fat, and it will be burned first. However the secondary energy reserve is muscle tissue which can also be burned for energy. From her body's standpoint burning muscle may actually make a lot of sense because muscle is an active metabolic tissue that requires calories just to maintain itself. So when her body burns muscle tissue, it not only gets some energy out of it, but it also lowers its future metabolic demands!

The second reason why normal people may lose muscle mass is because they stop exercising. When you are exercising, especially when resistance training, you are constantly destroying and rebuilding your muscles. Every time your body rebuild the muscle to be a little bigger and a little stronger because it anticipates future stress on it. When that stress doesn't come because you stopped exercising, your body doesn't have any incentive to keep the muscle in top shape and it gradually loses some of its size and strength. Note however, that this kind of muscle loss is typically much slower and much lesser in magnitude than muscle loss due to caloric deficit. In either case, rebuilding your muscle mass will be easier the second time around than to have gained it in the first place, so it's not a complete loss to build muscle and then lose it.

Now that you understand the reasons for muscle loss, it's pretty obvious how you can minimize it. First, eat enough to not lose weight and, especially, avoid crash diets with severe caloric deficits. Second, keep exercising, especially weight training.

In your case, one month without exercise will have very little impact on your muscle mass assuming you haven't lost any weight. You will probably become weaker, but it would be due to neurological reasons more than due to muscle mass loss. Your strength will return quickly once you start exercising. So don't worry about it too much,