Fitness Bores

It's great when someone gets into something, it really is (isn't it)?
If you are the person who is into that particular activity. Usually people start off their latest thing with great gusto and want to share it with the world to keep them motivated. Fair enough, usually they get fed up, give up, move on and shut the hell up but then there is the Fitness/Gym bore.
Nothing makes me want to rip my arm off and beat the shit out of someone more than when they go through their routine.
I am suffering such torture at the moment. Its a shame, this person is nice until they start spewing out their daily or more like hourly spiel. Every conversation can be turned around to their regime.
By regime, it goes through, when they went to the gym, what they did there in great detail, what they eat, how much they eat, how often they eat, how the food was prepared, how the food died, supplements etc etc etc AGRRRRRRR!!!!!!!!
Been going on for months. Even when I blatantly change the conversation back to the original it gets turned on its arse back to them spitting out verbal diarrhoea about how wonderous their new way of life is.
I hear "Look I am eating this, it is horrible but my trainer said I need to eat it" WTF
What struck me the most was that this person was an expert at everything after a few weeks, nutrition, how to use the gym equipment, even down to criticizing guys who had been working out for years.
Sheesh!!!how much of this shit do you need to listen to before you are allowed to stick your hand up to their face and say ENOUGH
Are you allowed to give them a slap if they don't stop?
Never mind. Tomorrow it's someones birthday and guess what? they WILL eat cake. Only after they tell us about the bad fats sugars etc that is in there.  It will be followed by an afternoon of look at me everyone, I am totally hyper because of the carbs and refined sugar.
Tomorrow may be the day I smuggle booze into my work in my water bottle.