The average IT office is really not a sporty place, and people also really don't like if you dress well either. It makes people feel threatened and annoyed.

What people like is for you to be a partner in crime in neglecting your health, having no self control, making self deprecating jokes and join them in unhealthy activities so they can feel less responsible for it.

People save their best self for free time and social life, where it actually scores some points, and show their less positive side in the workplace, and that's a bit of an unspoken rule that you're supposed to really relax at work.