Why do I always lose the ability to eat large amounts of food during a period of weight loss?

[jennifer_bloom]

I've dieted multiple times over the years and the first thing that happens each time is I lose the ability to eat high amounts of food, today I had 1/2 a chicken pad thai and was filled to the max to the point it was uncomfortable and before I began dieting I could eat 1.66 times a single serving of chicken pad thai and every time I did low carb for 6-8 weeks in my 20s I would only manage 1/3 or 1/4 of my previous portion sizes when I visited restaurants. Why does my body restrict my calorie intake ability first before burning actual body fat?

[Ευδεμονια]

That happens because our body in general is adapting to general conditions. If you make your body get used to smaller portions, your stomach shrinks and can widen less than before… that’s the point to have a diet: if you reduce by will your intake, your body with time will get used to it and requests less food to be full.
I lost 12 kgs from last year and the first way to to that has been reducing size portions… nowadays I can eat barely half the portions I ate last year and I don’t have hunger sensation anymore.

[DryGermanGuy]

That's very easy - your body adapts. During dieting it scales down to what it assumes will be your future intake. So later your stomach etc. do not react too kindly to large amounts of food.
It's the same with someone not drinking alcohol for a longer time. The first hard liquor will make him drunk very quickly.

[SiberFox]

Diets are worthless. What you need is a consistent nutrition plan.
Diet are bad because they are temporary. What is necessary is consistently having good meals. You can "cheat" and have junk food every now and again. But if 80% or so of your meals during the week are high quality you will most likely keep a good stable weight.