Hi ErickaR and welcome:

All of the information you need is on this site. This thread will give you the basics: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/. Start with the ‘Warnings’ post, then check the TDEE post for an explanation of how TDEE is involved. The ‘Really’ post will give you an idea of how weight loss can progress (it is not necessarily consistent).

The information on this site is really broad. Check out the various forum categories and keep up to date by looking at the ‘Recent Posts’ section of the Forum category at the top of the page. If you are looking for something specific, the search function at the top right of the page is helpful.

A low FODMAP diet may help with your IBS: https://stanfordhealthcare.org/content/dam/SHC/for-patients-component/programs-services/clinical-nutrition-services/docs/pdf-lowfodmapdiet.pdf

Good Luck!