Before I go any further I have to stick my hand up here and say I'm one of those people who can eat whatever they like and never gain weight, I'd actually like to gain a bit of weight but I simply can't (I can but if I don't keep up the excess eating I lose it again). I can lose weight but then I become painfully thin.
I'm with ChickenFarmer here - the laws of physics mean you can't get more energy out than goes in, hypothyroidism certainly makes it easy to retain weight but it doesn't add it.
When calories out (expended thru exercise and natural body functions) is greater than calories in, it's impossible to gain weight (except via fluid retention which can also be caused by hypothyrodism).
I think the key to any weight loss plan is honesty, honesty with yourself;
I used to work with an obese woman who was forever on a diet of some sort and yet she gained weight. She would always complain that despite eating virtually nothing she had gained however many pounds each week. He weight was becoming a health problem and she started to take more and more time off work. I asked the cleaners to collect her bin and keep it. Everyday it was full of chocolate wrappers, soda cans, sandwich boxes for Tuna Mayo or similar, all the stuff she was supposed not to be eating and that was just during work hours. I spoke to her about it, about the absenses really and mentioned the contents of her bin and she honestly told me, and I totally believed that what she was tell me is what she thought was happening, that other people must be putting empties into her bin. This continued for some time and she seemed to reach a point where instead of gaining a few pounds she was gaining huge amounts of weight each week until with her excessive absence record and her refusal to seek help I had to let her go. She simply didn't beleive she was eating what she was eating, she had somehow tricked herself into thinking she was sticking to the diet but it didn't work. It was really terribly sad.
I heard that about six months after we had let her go she was taken into hospital with a heart attack (she was only 30 at the time) but that she had survived and was receiving counselling. I never heard after that what happened to her but for sure if she continued on the path she was on, medical and simple physical problems would quickly catch up on her.
I'm not quite sure what point exactly I'm trying to make here, perhaps it's the old school adage of "If you cheat, you are only cheating yourself". There's no need to hide the fact that maybe you crumble one day and accidentally find yourself in MacDonalds ordering a Big Mac and you go 'supersize', one Big Mac isn't going to add ten pounds and being honest about it isn't going to lead you to need to hide any other indiscretions.
Obestity is a relatively new concept here, ten years ago it was rare to see someone you would even describe as 'really fat', but it's definitely become a popular choice now, particularly among children. Those children will almost never get back to a normal weight and even when they do they will struggle because of the stresses their young bodies have been through while growing and carrying twice as much weight as they should be.
Anyways I hope you get to where you want to be, or at least closer to it. Good Luck to you
