so, you have an over active thyroid and not a fast metabolism, glad we cleared that up.
You should seek some treatment for that.
I also knew you wouldn't post what you ate, reason is you totted it up and realised it was nowhere near what you thought.
People who claim 5/6000 cals a day seldom come anywhere near that.
Oh, and the pic you posted as a result of 3000 cals as opposed to 5000 clearly shows that if you were in shape at 3000 then eating 5000 would make you very fat in a few months and eating 3000 cals you would never have held onto that muscle if you have an overactive thyroid that burns off 5000 so easily.
Its not even convenient to eat so much food, most people who work dont have the time to eat all that every single day.
Well an over active thyroid results in a faster metabolism .. so yes I do have a fast metabolism although my thyroid is not the only factor for that.
No need for treatment since my thyroid hormone levels are still considered to be within the "normal" range just at the upper end.
I keep track of everything I eat (except for cheating days where I just eat whatever I want .. which often actually results in less calories than on a regular day) in a logfile and I have been doing this for nearly 10 years and trust me I can count. If you really want me to I can post a few days out of my logfile but it will be in German but you can clearly see that I'm certainly averaging 5000 kcal per day.
I do lose muscle when dieting just like pretty much everyone so of course I can't hold onto everything with less calories but it's not like I'm close to starving on 3000 kcal although I'm still very lean at 5000 kcal. I'm sure that the more calories your body gets the less efficient it becomes.. so even though I'm able to maintain quite a bit of muscle at 3000 kcal or even 2000 kcal does not mean I will get fat at 5000 kcal although I'm sure it would be the case for most people.
It's certainly not convienent to eat that much food and I don't think it's a gift to be honest - when I started working out my biggest problem was to get in enough calories to gain muscle. It would actually be pretty much impossible for me if I would be eating clean food all the time and at least 1500-2000 kcal are from shakes. My friends used to make fun of me since I would never leave the house without like 2 litres of chocolate milk with me.
I know tons of people who claim to eat huge amounts of food and not gaining weight and then when they really count their calories it's like 2500 or sth like that - but trust me I'm not one of those guys.