Hmmm... I get what your Mum's saying, but stabilising your IBS will make gaining weight so much easier.
There've been a few people on here before who've got seriously underweight...sometimes cos they scared of what food will do to them and so avoid it all. Is this like you?
You really can put on loads of weight and still eat IBS safe foods. Eating frequently is the key - and this is something that will help your IBS as I mentioned before. It's why so many of us on here need to LOSE weight - we've put loads on with this diet. Oops . Since getting IBS, I've GAINED 20 pounds. And that's without trying!
With trigger foods, it's true that not everyone has the same triggers. HOWEVER, the exceptions are just people who are lucky enough to tolerate some triggers, like maybe a little dairy. Heather has done loads of research into this. It's NOT just a fad-like diet.
Can you ask you Mum to log on to the board, so we can chat? You could set up a username for her so she doesn't have to bother with all that.