Speaking of overtraining, lets talk about the other kind of rest, the time between workouts. How much rest you need between workouts depends a lot on your experience level. Beginners can workout every day or every other day where as an advanced bodybuilder would have to wait 3-6 days between workouts. Please note that when I say that an advanced bodybuilder needs 3-6 days between workouts, I mean for a particular bodypart. For example if you are advanced and workout chest on Monday then you shouldnt workout chest again till Thursday at the earliest. Its fine to do legs on Tuesday, back on Wednesday though!
In other words, when you lose bodyfat, you lose some muscle mass too. Always . A bodybuilder in the final stages of contest preparation loses some muscle mass as she drops bodyfat. And when you gain bodyfat, you gain some muscle mass too. Always . A man sitting on his couch who gains 100 pounds eating chips and queso gains some muscle mass. More importantly, when you gain muscle mass, you will also gain a little bodyfat at the same time. You can skew the percentages in the direction you want with training, careful control of your diet, and anabolic steroids, but you cannot violate the Laws of Physiology.