Low Fibre/Low Reside Diet

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hello, I was just wondering if anyone here has to follow this type of diet? I have UC, IBS and IBD and this diet seems to go against everything I've been taught about healthy eating. I have to strive for under 10 grams of fibre per day, but looking at the options for what I can eat, It's hard not to get depressed about the lack of food choices. also, looking online for what foods are acceptable is very confusing because different websites and lists contradict themselves. Any advice or tips would be great. I don't know how I can switch from high fibre/whole grains and lots of fresh diverse fruits and vegetables to white flour, white rice and no raw fruits or veggies and not gain weight? Any tips would be great. Thanks!