So, long story short: My father has always been pretty overweight,

>>16991083
oy, bump.
I don't want my dad to die

He probably has some problems with the hormones that are responsible for satiety. Try to bring it up as the matter of health,maybe he will take it more seriously then.

Don't be overtly nasty about it, that only gives him an excuse to shield himself from the truth in what you say. I'd sit him down, if possible with family members present who support you, and say you're sorry for being rude about it but in essence you are sincerely very worried about his health and life span. Stress that obesity is a huge factor in some of the most common death causes. If he brushes this off like it does not affect him, try to get him to at least go to the doctor then so he can confirm that your dad is healthy and has nothing to worry about. The doctor will tear him a new one if he's any good.

>I tried fatshaming him

Despite what /fit/ says, fatshaming doesn't really motivate anyone, OP.

>>16991335
That's possible but it's also just a vicious cycle. Your stomach extends to adjust to the amount of food you eat and if you suddenly eat less then you're not going to get that full sensation.

>>16991348
He can cut down on food grudually so as to make it less painful. Stomach tends to contract when you start to eat less, so he will be fine if he doens't go overboard with a diet.

>>16991359
Sure, I just meant there doesn't need to be something medically wrong with him for him to only feel full after eating tons of food if that's what he did up until now. Though it's always worth checking of course.

>>16991083
Both my dad and mom are a bit overweight, but not obese. They don't actually eat much, rather its probably because their metabolism is slowing down. They just need to be more active - would also appreciate more advice on this.

>>16991083
>thinking of sticking this up onto every door which leads to food.
Strictly speaking, overeating is a compulsion that mimics additiction, rather than an addiction per se. The difference is that with addiction, the person becomes dependent on a foreign substance, while with this kind of compulsion, the person becomes unusually dependent on something the body produces itself.

The end result can seem basically the same, especially to the person who has it, but the treatments are different. They have to be. You can stop smoking or taking drugs, but you can't stop producing dopamine.