Holy shit. You're arguing my point, again. Fine. I'll dumb it down.
Three main kind of food. Protein, carb, fat. Protein just protein. Carb can be simple or not-simple. Simple bad, lots of sugar, little variety. Not-simple good, more variety, more nutrient. Fat can be good or bad. Saturated bad, make blood full of fat, make heart not work good, make body full of cancer. Unsaturated good, make blood less full of fat, make less cancer. Junk food have more simple carb, more saturated fat.
Body feel food-happy two ways. One, big-meal-good-blood-sugar body happy. Two, bad-junk-food meal, make brain happy.
If three main food type in equal balance, big-meal-good-blood-sugar body happy mostly same between healthy and bad junk food. However, bad junk food usually have more fat, more carb. More fat, more carb mean more energy per food, so less food for same energy. Less food mean small stomach. Small stomach mean less food-body happy. Also, more fat/carb mean less good-blood-sugar happy. Make hungry again sooner. Bad junk food also have more saturated fat, more simple carb. Make heart, blood, organs unhappy. Make cancer.
Brain-happy happen with bad junk food. Body like salt, like fat, like simple carb. Many fathers ago, salt/fat/simple-carb hard to find. Need to find to live. So, body decide to make brain very, very happy when find these things. Make feel more satisfied. However, now salt/fat/simpe-carb easy to find. Now people eat too much. Now they hurt body, heart, blood pressure, kidney, make cancer. user free to eat bad junk food as much as want, and if in balance, probably feel as/more full. However, bad junk food make user live less long. Probably good thing. Keep it up.
Sorry use big word before. Me expect people discussing nutrition actually know nutrition biochemistry. But me forget reading hard. Understanding hard.