Hyperstimuli are like regular stimuli, but turned up to 11. Fruit contains naturally occurring fruit sugars, which your body craves because sugar is an important energy source and fruit is full of valuable nutrients. Fruit is a natural stimulus. Candy is made from a vegetable, sugarcane, that has had all of the annoying fibrous vegetable part stripped away and been refined down to a pure, sugary, chemical substance. Running is normal; riding a rollercoaster is not. Chatting with your friends is a normal social interaction; getting a thousand likes on Facebook is not.
Most of us have happiness “setpoints” that we tend to return to after weathering the slings and arrows of fate and fortune. Some of us tend to be happy people, facing misfortune with confidence that things will turn out; some of us tend to be dour, facing happiness as a trial to be endured until misery returns. Of course there are exceptions and things that really do radically alter your life (“I’m not starving anymore! Yay!”) but for most of us, most of the time, will trend back to our normal moods.
This implies that the hyperstimuli in your life are not really making you any happier. Long-term, you are no happier eating hamburgers and pizza than you would be eating rice and beans, because you adjust to the presence of the hyperstimulus and downgrade to treating it like a normal stimulus. Pizza once a year is a feast. Pizza once a month is fun. Pizza every day is monotonous.
But once your brain is used to processing hyperstimuli like normal stimuli, regular stimuli look pale and boring by comparison. If you can have ice cream and cookies and hamburgers and pizza for dinner, why would you have rice and beans? Oh, sure, you know rice and beans are “better” for you. You have some sense that you’d weigh a lot less on rice and beans, and that you’d spend a lot less on food. You might even avoid a heart attack. Abstractly, these are all nice things, but rice and beans are boring. You don’t want rice and beans. You want pizza.
Of course, maybe if you’d never started eating hyperstimulating food every day in the first place, you’d think a good plate of rice with a side of nicely spiced beans was pretty nice.