Opinion: nothing. Our hunger/satiety signals are normal and evolutionarily advantageous. What changed was the access, and composition, of food.

Food is tasty. Like really tasty these days. High fat, sugar, salt. And it's super duper easy to get. This stuff is designed to perfect target your brain and make you say "mmm".

You wanting to eat more makes sense because these foods are highly, or over, nutritious. Cavemen didn't have fried chicken, they barely had chicken - they had nuts. This wanting to eat more and more is evolutionarily advantageous. Because you don't know when your next meal is. You should be greedy, eat as much as you can and as often as you can. I mean, look at dogs. Give them infinite access to foods and they will eat themselves to death. Sure we're smarter but much of this stuff is at a level below the brain.

For all of human history I'm sure this functionality was a very good thing. Now that we have food surplus... not anymore. And to top it off, for the first time ever, we don't need to move to live. People are sedentary. So we don't even offset this effect with movement.

It seems to me the human brain/body is incompatible with modern human life. We're broken. We're exploitable by addiction at every turn. The solution might be to change our brains. Ozempic seems to help a lot - less drinking and smoking too.