It`s called competitive bodybuilding !!
In the activity known as competitive bodybuilding, for the most part competitors train down to a low BF % to look their best on contest day..................... ...normally training down from what is known as OFF-SEASON condition or OFF-SEASON shape...... where one usually carries more muscle as well as water and fat........not excessive fat though................ve ry important point........not excessive fat if the competitor is halfway intelligent !!
Other than that, time is spent training heavier......... possibly in an effort to get bigger or just to eat more like an athlete and not a Spartan counting every gram of food intake on a daily basis for 16-20 weeks which can be brutal.
This extra water and fat helps to provide more energy as well as protecting the joints, ligaments,and tendons when training heavier as most OFF-SEASON bodybuilder have a tendency to do......hoping that the heavier poundages used may result in a bit more muscle size when they next compete.
Everyone from Arnold to Ronnie has done this......no one stays in contest condition all year long.........no one!!
You sir are just lean ,you are far from being in contest condition by a long shot..................yo ur daily diet is atrocious and your lean body is simply the result of a fast metabolism and the use of GROWTH HORMONE.
That is all.