A lot of "fitness trainers" are full of shit. I know; I work with them. Fitness trainers are often times clueless about diet. They are "certified" to design fitness programs not diets.
I agree. You don't even need a degree to be a fitness trainer, just be certified. When I first joined the gym, they were pushing hard for me to buy the package with personal trainer. I guess this is because I got the deal through Costco, and not through the actual gym so they weren't making much off it. I looked at the trainers...exactly what I thought. Guys in spandex shirts with love handles and beer belly, just big arms. Like I would pay $100 per session for those guys!
You need to go to a nutritionist for a proper diet consultation IMO.
I have a friend of mine who was relatively small...5'8'', always around 145 lbs. He wanted to bulk up so he started lifting like crazy and take protein drinks and stuff. He got up to be around 180 lbs within a couple of months. The dude was built, looks like smaller version of LL Cool J or 50 Cent, lol. He got injured at work and couldn't visit the gym for a while, and he lost all that muscle fast and went down to 145 lbs.
I have no idea on the supplement stuff so I can't say anything about it, just posting up what happened to my friend.