If you want to be successful in your quest for a healthy body weight, meals take planning. I suggest finding a day or two during the week that you will always set aside to prep your foods.
In this picture I have marinated tilapia that I am wrapping in plastic wrap to place in the freezer. I realize that it only takes minute to take some fish out of the freezer then cook it, but I am just like the rest of the world, and the thought of coming home to a plain piece of tasteless white fish is not attractive. Plain, boring fish also makes it much easier to come up with a fairly lame excuse for going out, ordering take out, snacking on junk or just eating something that I really shouldn't.
I buy a large amount of fish, then marinade it all at once, in a couple different marinades, overnight. The next day I weigh it out in my portions (I weigh out 5 to 6 ounces uncooked), then wrap each portion in plastic and put them all into a freezer bag.
If I remember to take a portion out before I head off to work, that's great. If I forget, it will defrost in a very short period of time, usually as I prepare the vegetables, set the table, warm the rice, it's fast.
Tilapia, and most mild fish can easily and successfully be microwaved. Purchase a domed lid or use a plate to cover the cooking dish, never microwave plastic wrap.
I will place the fish and some water or broth in a shallow bowl and microwave it a few minutes, then place the fish on the rice and vegetables and pour the cooking liquid over as a sauce.
A lean, muscular body doesn't happen by chance, you need to make great efforts to get it to a state it would rather not be in! Be prepared at all times.