Let's talk about gaining and losing weight for a minute, and what "realistic" goals consist of, and how to potentially stay out of trouble doing it. The big problems here as most of you have either experienced or watched others get into trouble doing is either trying to add mass to fast (read that, getting FAT) or dropping fat to fast (read that losing muscle.)
Lifter A decides it's damn strait time he sees what's underneath that layer of bodyfat he's been hiding under for so long. He didn't gain it all overnight (OK in some cases yes, the lifter does, but we'll get to that in a minute) but damned if that isn't going to stop him from trying to dump it all overnight. Sooo…..the crash diet begins. Week one he drops 5 lbs and is elated. Week two he drops 4. And a week later another 4, he keeps this up figuring it will take no time at this rate to be sliced and diced and the king of the beach........but......since he is carrying so much bodyfat and not doing any precision testing to determine how much bodyfat he is losing vs how much muscle he really can't see how badly he is catabolising his body. At this rate he is probably losing at least a 50-50 fat to muscle ratio....bad news in any lifters book.
If the trainee diets using the correct macro-nutrient profiles, and isn't too aggressive with cardio they should at least be able to build a little muscle while dropping bodyfat and strength should go up the whole time. If you are a 150-200 lb trainee figure about 1-1/2-1-3/4 lbs fat loss per week 200-250 2-2-1/4, and the big boys 250+ can often get by with 2-1/2+ per week without catabolism becoming a problem.
Lifter B decides its time to get serious about adding mass and to that end decides it time for some serious eating. Well he often ends up right where lifter A is PRONTO. If you are new to PRODUCTIVE training using volume and frequency correct for YOU and have never experienced the "first time" gains most people make when they start training you may add 20-30 lbs to your frame in a short while. If you are past this point, it's time to get real and understand the gains will come at a much slower pace. If you are a natural trainee that has already experience the "newbie" gains and are adding more than about a lb of scale weight a week, I'll betcha your getting fat doing it.
And if you are doing a cycle DON'T expect to add 30 lbs of muscle. Regardless of what the unknowing are posting and you reading. Yes, first time users of a good solid cycle (not these damn 2 week specials that are in vogue now) MIGHT put on 30 lbs, but 15-20 solid lbs is much more realistic. Most of the guys you see posting about 30-40 lbs of muscle just ate their way fat.
This post is not going to be a "how to", but a "what not to do". Don't let the above scenarios be you.