I'm surprised you would ask this. You've been here for a while. This is usually a newbie question. But then again, I'm always re-reading DANDR and I always find something "new" after 9 1/2 months of LCing. But yes, the TOM causes weight gain (mostly through water retention). I put on 2-3 lbs. before, during, and just after the TOM. I've seen other posters refer to gaining 5-10 lbs. But, it all disappears afterwards. Some posters even experience a little whoosh afterwards (although I have yet to). Best advice, DO NOT GO NEAR THE SCALE right before your TOM!