If eating 5 meals a day is the fastest way to lose weight,y do gastric byp/lap band surgeries work so well?

The basic idea behind these surgical procedures is to reduce your stomach size so that you feel full all the time, DRASTICALLY reducing the amount of food you're eating (next to nothing). Based on the theory of eating 5 small meals a day, I hear that if you eat next to nothing your body will go into "starvation" mode and hang onto the fat very effectively, making it very hard to lose the fat. This is against conventional wisdom, which says if you want to lose weight, stop eating. So how come these surgeries, which force you to eat next to nothing, are so effective in losing weight? Is conventional wisdom correct?