Being pretty inactive in participating in extracurricular activities during my BA, I have decided to compensate for it now, durin my job. Won't adcom members conclude that I do this only for MBA thing? Does this somehow reduce my chances of getting admitted?
Delayed_flight,
They may suspect that your extracurricular motivation is not pure, but at the end of the day what matters is the quality and depth of that involvement. So start as early as possible, find something related to a genuine interest of yours (not a 'usual suspect' charity/NGO), take a leadership role (e.g., rather than being a volunteer mentor, coordinate the efforts of a group of volunteers, or sit on a board, or start an NGO of your own), and throw yourself into it so your impact stories are strong (i.e., so you can show impressive results). With extracurriculars, adcoms care more about duration, depth, leadership and impact than why you got involved.
Good luck,
