I would to some extent agree with the practice what you preach comment, but not completely.
I mean what if someone has a Wheat allergy, should they never come on here, and advise people to include Whole-grain in their diet? Or what if you're Lactose intolerant, never tell people to eat Yoghurts, or low Fat Cheese?
Heck I advise people to eat some stuff I don't, but usually I won't eat those things for reasons like smell or taste, or in some cases principles, but I'd still expect, if I think someone might benefit from considering low Mercury content Fish, as a possible diet inclusion, they would, not respond with, "you don't eat Fish, so don't say I possibly should fella. Damn hypocrti", or something like that.
I admit though, people who are overweight, shouldn't potentially work in gyms at all as trainers, unless they have an LBM, BMI within a set range, as it's a bad advertisement for the Gym. Not being fattists, but how many overweight people would trust advice from people who look a bit like them?
In regards to diet though, well I don't think Gym instructors should be admonished, if they are in some cases people giving diet advice, (some probably aren't expected to), and then caught eating a lunch of White Bread Sandwiches with full Fat Mayo on for example, and not a Chicken and Broccoli Lunch instead, as we don't want to be too harsh, because Gym instructors and PT's are humans too, not massive rolemodels who represent everyones hopes and dreams, like sportspeople and actors are
. I'll keep him in prayers.