My vote is for hormone disruptors in the food supply. Plastics. If you look at the upswing in obesity, it happened about the time plastic food containers became ubiquitous. Its a nice theory, anyway... Hormone-mimics In Plastic Water Bottles Act As Functional Estrogens
It's both, but lazy is more common than genetics... In my job, I see both. Today I had the pleasure of hauling around a 410 lb patient who just didn't give a fuck. She had the worst attitude ever and every medical problem under the sun due to her weight, but her morbid obesity was caused by nothing more than her need for extreme excess. My back still fucking hurts. But. I often come across people who have issues with their thyroids, go years and years of packing on the pounds and trying their hardest to lose weight to no avail, with no idea that there is even something wrong. They blame it on themselves for not being able to lose weight, and most don't even have any idea that it is actually something medically wrong until they go to the doctor for some seemingly unrelated symptom and the doctor runs a thyroid panel.
Watch some old movies filmed in the 50s. See many fat people? Only a few. Ok, that could be biased so go ask somebody who was there. They'll tell you that back in school there was a fat kid in class but not anything like today. You don't see an evolutionary change like that for many thousands of generations so it's certainly a lifestyle change that has occurred. Basic math, if you consume X calories and expend Y calories and your body weight increases (at 3500 calories per lb) Y < X. If you gain 1 pound of fat per week you must either burn 3500 more calories or consume 3500 less per week to maintain your current weight. metabolism comes into play as well as many other factors so just remember... wait Its my turn. Eat more and do less get big. Do more and eat less get small.
dude im reading this thread at the peak of my high and let me tell you that shit sounds stupid and funny at the same time