I have experienced intense cold, fatigue, drowsiness and irritability when I have previously been on a low calorie diet for about five or six months -- during which time I was taking daily vitamins, extra B vitamins, and supplements. Also, I was increasingly and never-endingly hungry. After I gained back all the weight (plus additional pounds) all these very-difficult-to-endure symptoms went away. I later learned that these are typical physiological responses to severe dieting, when the body goes into starvation mode. I understand that bariatric surgery relieves hunger, but what about these other symptoms? I had no energy to exercise whatsoever, even though I was losing considerable weight. By the way, my thyroid and sugar levels are fine.