after our malabsoprtion ends, our bodies become extremely efficient at holding onto every last calorie we put into it, making regain easy even if our calories in=calories out? 

With RNY, you do lose the calorie malabsorbtion (but you keep losing vitamins, so never slack on those). 

I know that prior to my DS, my doctor followed me on many diets, and I had a history of extreme diets and fasting. She told me that I had definitely damaged my metabolism (genetics probably was part of the issue too, though), and that if you have done it once or twice, you can somewhat re-set it, with careful eating (no severe calorie restrictions) and consistent exercise. 

When you have a history of doing it over and over, as many of us do from dieting, it's not really fixable, which is how I ended up with a DS.

Lots of RNY folks regain, and that may be an issue, but there are other things, like if you are already efficient, then once you lose the calorie restriction, you are back where you started before surgery. I wonder too about stomas that get stretched, when people complain that they are hungry immediately after eating, and have no restriction. Food moving quickly into the intestines, then making you hungry too soon would have to be an issue. 

It would be good if there were more studies specifically on this, as I know I read everything I could find when I was researching surgeries. 

I assume you're talking about the RNY specifically, because VSG and Lapband don't have any malaborption and DS malabsorption doesn't end.

Actually though, the answer to your question is that with ANY caloric restriction, whether WLS or "just" a diet, our metabolisms become more and more efficient.  That's why so many of us say we "dieted our way into morbid obesity."  The less you eat when dieting (or starving post-WLS), the less you CAN eat later.

Yet another reason the DS is better!

Here's some science for you:

http://ajpregu.physiology.org/content/290/6/R1577.long (the discussion is both enlightening and depressing)Am J Physiol Regul Integr Comp Physiol. 2006 Jun;290(6):R1577-88. Epub 2006 Feb 2.

Peripheral metabolic responses to prolonged weight reduction that promote rapid, efficient regain in obesity-prone rats.

MacLean PS, Higgins JA, Jackman MR, Johnson GC, Fleming-Elder BK, Wyatt HR, Melanson EL, Hill JO.

Source

Center for Human Nutrition, Department of Medicine, University of Colorado at Denver and Health Sciences Center, PO Box 6511, F-8305, Aurora, CO 80045, USA. [email protected]

Abstract

Weight regain after weight loss is the most significant impediment to long-term weight reduction. We have developed a rodent paradigm that models the process of regain after weight loss, and we have employed both prospective and cross-sectional analyses to characterize the compensatory adaptations to weight reduction that may contribute to the propensity to regain lost weight. Obese rats were fed an energy-restricted (50-60% kcal) low-fat diet that reduced body weight by 14%. This reduced weight was maintained for up to 16 wk with limited provisions of the low-fat diet. Intake restriction was then removed, and the rats were followed for 56 days as they relapsed to the obese state. Prolonged weight reduction was accompanied by 1) a persistent energy gap resulting from an increased drive to eat and a reduced expenditure of energy, 2) a higher caloric efficiency of regain that may be linked with suppressed lipid utilization early in the relapse process, 3) preferential lipid accumulation in adipose tissue accompanied by adipocyte hyperplasia, and 4) humoral adiposity signals that underestimate the level of peripheral adiposity and likely influence the neural pathways controlling energy balance. Taken together, long-term weight reduction in this rodent paradigm is accompanied by a number of interrelated compensatory adjustments in the periphery that work together to promote rapid and efficient weight regain. These metabolic adjustments to weight reduction are discussed in the context of a homeostatic feedback system that controls body weight.

Thanks for the insight and articles!