The reason why our satiety mechanisms don't work is because carbs upregulate insulin, which supresses leptin [1]. Leptin and ghrelin are the two main hunger hormones; leptin tells our brain we're full. The signal doesn't work too well in the presence of high insulin, and gets worse with insulin resistance, causing people to have a "second stomach" for sweet foods.

https://olumialife.com/knowledge/how-does-insulin-affect-lep...