If you are human ... You were born addicted to sugars and fats. If you eat too many sugars and fats you will get fat. Go ahead and blame food companies for stuffing your face with Moon Pies and washing them down with RC Cola ... It with probably help you lose weight.
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If you eat more than you utilize and burn off you'll get fat. Eat 3000 cals a day but only burn off 1000, 2000's going to storage in the body, usually as fat. But fat, protein, and carbs burn at different rates. Think it's protein, carbs, then fat will be burned off in order.
Food today has so many calories, so much fat, salt, and sugar that's it's literally impossible to burn it off unless a competetive athlete of some kind. Single McDonald's milkshake has I think 800 cals. That's an entire meal. And yet it's only the beverage part of a McDonald's meal. And since it's almost entirely sugar, which'll turn into fat inside the body, if you're drinking that every day plus all the other crap it isn't difficult to see how you're gonna get fat. As illustrated well in "Supersize Me."
Eating in the US has become a recreational activity and stress mangement activity. We're under so much stress in our society from any number of factors than managing that stress via pleasure is what many do. Some exercise, some drink, some eat, some have lots of sex. But when a society overvalues the wrong things, and undervalues the right things, as we do in the US, imbalances are created. Instead of encouraging bodily pleasure and intimacy we demonize it. Bereft of such a basic human need as touch and intimate contact we turn to alternatives not demonized, like eating and subtance abuse.