well for one thing it's down to nutrition. people aren;t getting enough and its making them more hungry. you go to any store and there are thousands, if not millions of packets of microwavable convenience so called 'healthy' 'diet' food that actually makes people crave more food. diet sodas are also linked to obesity. it's not necessarily a choice coz some of these foods look great and healthy but are nutrient deficient and makes the person crave more of this nutrient deficient so called food. if they got the right nutrient dense food to begin with then obesity wouldn;t be a problem