"Controversial -- Malabsorption has NOTHING to do with RNY weight loss!"
This post begins starts off with an extract from a previous thread re ghrelin. In that thread, a discussion arose over whether malabsorption is relevant to proximal RNY weight loss. Based on the research I think that, despite what most people are told by their surgeons, malabsorption has little to nothing to do with long term RNY weight loss (see below). I thought this discussion might be worth continuing.
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Brian121
Post Date: 10/1/11
...RNY patients lose more weight than do VSG patient (not because of malabsorption, which studies have shown is irrelevant to weight loss for proximal RNY despite what most surgeons think), but because of a dramatic increase in energy expenditure (think metabolism) that RNY offers -- but which VSG and the band do not.
Based on the research, here is the ranking between these 3 surgeries:
(1) RNY
- drastically increases resting energy expenditure
- slashes appetite
(2) VSG
- slashes appetite
- no increase in resting energy expenditure
(3) Band
- INCREASE in appetite
- no increase in resting energy expediture
This is why RNY patient will lose the most weight, VSG the second most, and Band patient very little long term. Restriction plays, at most, a modest role in weight loss (and arguably very little). Again, malabsorption of calories plays virtually ZERO role in proximal RNY weight loss (see 2009 Harvard study).
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****rogirl
Post Date: 10/1/11
Do you have a full citation for the "2009 Harvard study" so I can look it up?
Everything I have seen in ALL of the medical literature indicates that the temporary caloric malabsorption of RNY is a KEY component of the initial weight loss. If malabsorption plays no role in the intial weight loss, why would surgeons bother to do the bypass portion? Why not just create a pouch instead of a sleeve and be done with it?!?
Can you also explain on what you base the indication that RNY "drastically increases resting energy expenditure" whereas VSG does not? I am unaware of any way in which RNY increases your metabolism. The appearance of increased metabolism is a result of the caloric malabsorption (which you are indicating is not a factor).
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Brian121
Post Date: 10/1/11
...here is the 2009 Obesity study (forgot to include it in initial set) by Harvard Medical School and Massachusetts General Hospital:
www.nature.com/oby/journal/v17/n10/full/oby2009207a.html
You will see it shows that the pair-fed subjects lost about 1/2 as much as the RNY ones, and this was solely because of the drastic increase in energy expenditure seen with RNY in the fed state.
As to your question as to how this could all be possible if restriction is not a dominant player, consider the following. When an insert is placed into the duodenum EndoBarrier patients lost an avg of 50 lbs (http://www.prweb.com/releases/2010/09/prweb4482324.htm) without any stomach restriction. This insert also cures diabetes, high blood pressure, high cholesterol, high triglycerides, as with RNY. The insert moves absorption of calories from duodenum to further downstream in the small intestine. That does not equate to malabsorption, just further downstream. The process of absorbing calories further downstream triggers a host of hormonal and metabolic changes also seen in RNY. Unfortunately, they won't let you keep the insert in permanently, so it is not currently a great lifetime option. But its efficacy supports the fundamental reasons for RNY success.
The reason RNY is so successful is because it addresses two key root issues -- (i) it increases energy expenditure in response to eating and this increase does not diminish with weight loss, something lost in morbidly obese people and (ii) it suppresses appetite. So, RNY fundamentally shifts the homeostasis in our favor.
As to how RNY could increase energy expenditure, again, it has to do with shifting absorption of calories to further down in the small intestine, where proper hormonal signaling can occur. Many researchers now believe morbid obesity (and likely diabetes and metabolic syndrome) is fundamentally a disorder of the duodenum (first part of small intestine). Some believe (and my view) that this disorder is characterized by too efficient an absorption by the duodenum, leaving too few calories to be absorbed further downstream in the small intestine. My own view is that this was an evolutionary adaptation to long term starvation in certain peoples, and this might be supported by some indigenous populations with incredibly sparse food availability who rapidly become incredibly obese (> 500 lbs common) and rapidly become diabetic when entering western society.
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Brian121
Post Date: 10/1/11
Relevant excepts from the 2009 Harvard study:
"A growing body of evidence suggests that profound changes in body weight and metabolism resulting from GIWLS, and particularly RYGB, cannot be explained by simple mechanical restriction or malabsorption (12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27)."
"This procedure effects weight loss by altering the physiology of weight regulation and eating behavior rather than by simple mechanical restriction and/or malabsorption as previously thought."
"Although we observed a small decrease in nutrient absorption after RYGB in this model, there was no evidence of clinically significant malabsorption (36)."
Note that the VSG surgery was also performed in this study for comparison, and it did not exhibit the increase in energy expenditures seen in RNY, nor was it seen in pair-fed subjects (given exact same small quantities of food as RNY subjects, just without the surgical modifications of RNY). So caloric restriction does not remotely account for the drastic increase in energy expenditure seen in this study.
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poet_kelly
Post Date: 10/1/11
An insert that moved absorption of calories downstream would indeed lead to malabsorption, because part of the small intestine would be unavailable for absorbing calories, just like it is when part of the small intestine is bypassed surgically.
I think the reason so many lap band patients don't lose very much weight is that they have difficulty getting the right amount of restriction. If there is not enough fluid in the band, then they have no restriction. But if there is too much fluid in the band, it is too tight and causes vomiting and other problems. It seems to be difficult to get just the right amount.
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Brian121
Post Date: 10/1/11
No, that is not correct. I know it intuitively may seem that way, so I don't mean to sound critical, but the now proven fact is that proximal RNY does not produce any significant caloric malabsorption (likewise re the insert example).
The reason that there is no malabsorption is that the later parts of the small intestine are more than up to the task of absorbing the extra calories they will receive (though maybe not 100% of nutrients) after the duodenum is bypassed. And by receiving these packets of calories (as would occur to some degree with healthy, thin people - but not the morbidly obese / diabetic), the parts of the small intestine that are downstream of duodenum perform their proper hormonal and physiological signaling, and THIS is a big-hitter as to why RNY cures not only obesity, but diabetes and the constellation of associated metabolic disorder (high blood pressure, high cholesterol, high triglycerides, etc). And as noted, RNY also addresses the homeostasis via controlling hunger, satiety signalling, and pleasure responses, further adding to its efficacy in long term weight reduction.
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on 10/1/11 7:33 am - riyadh, Saudi Arabia
The fact is once I stopped the Irn pills for a mininum of one week I feel dizzy and tired, this is my personal experience with many regards.
