answer:Most of your nutrition needs are collected and passed to the blood stream through your small intestine; the stomach is there for processing (digesting) to pass onto the small intestine. By reducing the size of the stomach, there is a smaller amount of food that can be handled, plus one gets full very quickly. People with smaller stomachs do feel full. But they get plenty of nutrition because they are still eating plenty to live on. What bariatric surgery doesn’t address are the psychological reasons behind over eating. That still has to be overcome. A person who has his stomach stapled may feel physically full after eating, but is still emotionally hungry for more food. A guy here at work lost about 150 lbs after having lap band surgery. But his drinking has gone up and he has regained about 30 lbs. And while he can’t eat as much, now all he eats are foods that are heavy on sugar and fat.