I imagine WW foods would be difficult for someone with IBS. I lost 10 lbs in less the. Two months by eating foods that my body could handle (and no activity or exercise involved). I gained 30 lbs in a few months due to being very sick with IBS and not knowing it.
I recommended finding what foods and drinks are your triggers. Months after diagnosis and I still chart what I eat and how it makes me feel. Mayo isn't a normal IBS trigger but it makes me sick. So does coffee and very high amounts of caffeine. High Fructose corn syrup and corn syrup make me ill. Cutting out these out helped tremendously. Like PP overly processed good doesn't sit well with me either.
I used this list to find out if they triggered symptoms.
http://www.ibsgroup.org/brochures/fodmap-intolerances.pdf
sorry on my phone so can't make clicky. Almost everything that can be a normal trigger for people with IBS is a trigger for me.
I wouldn't wish IBS on anyone. Good luck.