cassiecass,
I am hypothyroid and have been dealing with it for 20 years, more than UC. They had an extremely hard time getting my medication adjusted after my surgeries for over 18 months to the right levels. Having the wrong level can affect so much, weight, energy and hair loss to name a few. I suggest you do not go on a diet under 1,200 calories a day. I'm not a medical professional I've just been on a lot of diets. When we go on diets too few in calories our bodies go into a sort of protection mode and learn to live on less which defeats the purpose. I was on a 900 calorie day a diet more years ago than I care to count
The diet company (plan) I paid to go on that diet with went out of business a few years after I was on it. Subsequently what I found out is it is not good to starve your body. I do not mean to put down Jan Dollar's diet but as she stated she was on a specific diet for her medical problem.
I'm guessing your current weight gaining might be caused by lack of exercise, just because that is my problem. I can tell you to walk more etc. but I'm not doing it myself. I have remaining pain and other health problems and am not exercising myself..
I have changed my diet to include making myself eat my fruits and veggies by making a protein smoothie each day using the product PlantFusion daily. I also eat Greek yogurt, eat a deck of cards size of meat serving a day and try to eat beef only once a week. I love mashed potatoes and baked chicken. I also eat bread, crackers and cheese. Somehow I am maintaining my weight while not exercising at all. I lost 65 lbs after my surgeries, that I had gained from prednisone and still need to loose 15 lbs to be at a normal BMI. I am not trying to loose weight, maintaining is fine because I still feel like hell.
My main message to you is to not starve yourself plus eat plenty of good protein, no fried foods and get in your fruits and veggies. Take care and good luck.