any truth to this?

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

I don't think so.  Why would that happen?  Physiologically, how would it happen?

And if it did happen, how is it that so many of us are maintaining our weight loss several years post op?

Not sure what you mean by calories in = calories out exactly.  If you eat 3500 calories more then you expend you'll gain a lb, expend (use) 3500 calories and you lose a lb.

I don't buy into the whole "extremely efficient" although I do believe the malabsorption dissapates tremendously in my personal experience I do malabsorb some, just do not know how much that amount is.

I'm 6 1/2 years out and I had gained 7 lbs above my goal weight and was able to lose it fairly easily (less then 3 weeks) by going back to eating as my surgeon suggested should I see any regain. 

We are all so individual in how we lose, how much, bounce back or not, regain or not.  It's imperative that we each stay on top of our choices.  I strive to make good choices 80% of the time and when I see the numbers going up I change my eating and have been able to maintain fairly easily so far.

What apparently happens to SOME people is that their metabolism (which may already be wonky from years of dieting) can become permanently lowered because of the severe reduction in calories during the first 6 months or so post-op, so then it is SOMEWHAT easier to gain weight because of the lowered metabolism.  I have never heard anything about it being "super easy" to gain.

Whether that is true or not, I do not know.  I have heard it from two different bariatric surgeons, but have not been able to find any studies on it.

Personally, my guess is that that your body does not change at all... it just SEEMS like it does in comparison to the period of malabsorption.  After having the malabsorption for so long, I think it just SEEMS like you gain weight much more easily than you difd pre-op because you are used to losing and having the malabsorption and forget what it was really like pre-op.

Lora