I've been researching the differences between the bypass and sleeve options and it gets really confusing! My understanding from most studies is that you can achieve comparable weight loss over the first couple of years with either. But, since I have such a long history of losing large amounts of weight and gaining it all back and more, I am really concerned about choosing the one which will give me the best chance of keeping the weight off for the rest of my life.

So, from all I have read so far, the biggest difference between the way bypass works and the sleeve is, that although both restrict intake and hunger, the bypass also changes absorption. So - I assume this means that if I get to the point 3-4 years down the road where I can consume 1000 calories a day with either (which several sites suggested is typical), fewer of those calories will actually be absorbed with the bypass than with the sleeve. Is this correct?

My biggest fear is that if I go for a long period of time eating less calories - which will happen with both - will there be a time when my body thinks it is in that starvation mode again and switches back to that horrible place of being able to gain weight at a much lower calorie level than normal. For example now, I might normally eat 1400 calories a day, but if I want to lose weight so I might eat 1000 calories/day for a few months. Then if I start eating 1200 calories/day, I gain all that weight back! Is there that same "diet rebound" with WLS in general or not? If not, why? And if so, is there less of that with bypass because your body just doesn't absorb as much ever again?

I read somewhere that there is no such thing as starvation mode and that our bodies do not adjust to maintain on whatever reduced caloric level we maintain. Those studies may convince others, but I'm not persuaded. I have experienced what you describe more than once.

Because of that, I was afraid to get the sleeve or a bypass. I thought the initial year of extremely low caloric intake was unwise and would not lead to permanent weight loss. But after researching and reading so many success stories, I realized that even if a super low calorie diet isn't the perfect solution, when you combine it with bariatric surgery, for many people it works for the long term.

I think bariatric works because while you have some months with little or no appetite, you can train yourself to make better food choices and make that your new normal. You also realize that you need a lot less food than you previously thought. No solution works if you don't work with it.

I believe either surgery can result in good long term weight loss. But for me, the malabsorption of the bypass was a negative, not a positive aspect of the surgery. I am 60 and I thought the effects of possible malnutrition might be drastic at my age.

"Weight loss" via calorie deficits is one factor to consider;

the "malabsorbtion" of trace minerals is far more important in the long run.

Considering the total barrage of information on line, both factual & not so much, I urge considerable research of published peer reviewed studies of long-term with good controls and follow up reviews.

My brother had one of the very early gastric shortening surgeries circa 1964, due not only to his morbid obesity, but also resulting from the complications of a service related gut injury on battle field.

They didn't really understand the absorption of trace minerals in those days. Having a large portion of his gut removed did produce a long term 'malabsorbtion' which gave him considerable other problems quite difficult to manage.

Consider the nutritional needs other than weight related to insure you have the information to best make your decision.