When I meet people interested in being trainers or strength coaches I give them a challenge.  It is to do the opposite of what they enjoy in the weight room or what they are good at. Thick powerlifter proud of his bench? Time to get down to 6% bodyfat. Super ripped guy who loves his abs? Time to get your squat to 500lbs.
The reason is this: How can you tell someone how to lose fat if you can’t do it? How can you tell someone to lift heavy if you have never done it? It is like a doctor telling you that you are unhealthy as his hands rest on his beer belly. If you think you are a good trainer then what you should be able to do is gain 30lbs and then lose it and be right back where you were. Or get super lean and come back stronger than before. Trust me, once you have experienced the effort it takes to get very low body fat you will have a much better approach with your clients. Who knows? You might actually have trouble. What you think will take 3 months may take 6. If that is the case perhaps you have been leading people down the wrong path. No matter what you will learn a lot about yourself and your craft. If you want to take it more extreme then do an actual competition. Bodybuilding, powerlifting, weightlifting, whatever. If nothing else it is something to add to your resume.

Here are a few hard truths you will have to deal with…

To the strong thick guy: You are 240lbs. Your shirts are tight, you move serious weight in the gym. Diet down? No problem. You will end up a ripped 220.
Reality: You are going to be under 200lbs and be amazed at how fat you actually were.

To the ripped guy: You could be really strong if you wanted to but you like to stay lean. You like to take your shirt of when the opportunity presents itself. You could squat just as much as that guy if you were fat too.
Reality: You will have way more trouble gaining weight than you think and the strength will stop coming at some point until you learn how to train for strength.

Note to females: Admittedly, guys can get away with packing on mass much easier than females in society. The solution is just don’t take it to such extremes. Get a bigger butt at the cost of some lbs.  Lose your thick legs you subconsciously chalk up to genetics.  Plus you are professional. You can gain weight for a few months then take it off again no problem right?

“But my clients expect me to be lean.” Tell them what you are doing. You aren’t going to break any hearts. Note: They shouldn’t know how lean you really are. Keep your clothes on at work.
“But my clients respect me because I am big and strong.” No they don’t. Lots of people are bigger and stronger than you. They respect you because of your training knowledge. Also Newsflash: You are fat.
“But my clients are female like me and they want to be lean like me” No. They want to be lean regardless if you are or not. PS. You have no ass. Grow one then lean out again. THEN they will want to be like you.

Now the excuses are out of the way. Good luck.

This is a project that will take months not weeks.  Don’t half ass it.  Make a goal and get there.  If you do this and document the process imagine the power you will have next time someone says “The diet you gave me is impossible”. Take out a before and after picture of yourself. It’s worth a thousand words at least.