Re: APPROX. HOW LONG DOES IT TAKE FOR A GASTRIC BYPASS STOMACH TO DIGEST FOOD?

Hi, Tracey,
     This is quite a complicated question to answer.  Although I am a 
Ph.D.-level nutrition person, I decided to talk to one of my colleagues on 
the faculty here at the University of Hawaii at Manoa.  Dr. Sahar Zaghloul 
is also a nutritionist, but she is, in addition, certified to be a medical 
doctor (pediatrician) in her home country of Egypt.  I was able to talk 
with her this afternoon, and now I feel more comfortable in answering your 
question.
     My problem with answering is that it depends on how the gastric 
bypass operation is done.  The problems with digestion depend on which 
part of the stomach is left to be functional. The amount of stomach that 
can be left varies from about 1/2 a stomach to a small pouch about the 
size of 1-2 fingers.  However, if the part that is left comes from the 
upper stomach (as was the 'fashion' when I was studying nutrition in the 
mid-late 1980s), then one of the major problems would be 'dumping'of the 
food into the small intestine, simply because of stomach overload and the 
inability of the stomach to completely digest (break apart) the food as a 
larger, whole stomach would.
     With some of the more severe types of gastrectomy (cutting out of 
stomach), there can be only a small pouch (the 1-2 fingers-worth).  The 
patient may lose the parts of the stomach lining that produce the enzyme 
pepsin (a protease...helps digest protein) and the secretion hydrochloric 
acid (also helps with protein digestion).  Thus, when the partially 
digested food reaches the small intestine, the protein in the food may not 
be completely ready for further digestion...and may cause too much water 
to be drawn into the small intestine...and diarrhea can result.  Also, 
there is the risk of the 'dumping' that I mentioned before, because of the 
smallness of the stomach and the insufficient opportunity for the food to 
be mechanically broken apart. There can also be a problem with vitamin B-
12 absorption later on in the small intestine, because the intrinsic 
factor produced by the lining of the stomach may not be made...and this 
protein compound is necessary for transport of B-12 through the digestive 
tract to the right place to be absorbed, in the small intestine.
     Regardless of the type of this operation, it should NEVER to be 
undertaken lightly...it is dangerous surgery, and can be life-
threatening.  However, if a person is morbidly obese (where the degree of 
overweight, itself, is a threat to the person's survival), then sometimes 
it is the only solution left...all other attempts at losing weight have 
failed.
    Whenever there is a problem with digestion (mechanically and 
chemically breaking apart food in the gastrointestinal tract), there 
usually is a following set of problems with absorbing nutrients from the 
food-stuff into the body.  For example, if the fat in the food eaten 
hasn't been broken apart (mechanically) well enough in the stomach into 
very small lipid/fat droplets, then the enzymes that come from the 
pancreas and from the small intestine can't complete the digestion of the 
fat.  That means that too much fat-like substances get down further into 
the large intestine...this creates greasy stools, which can be a 
nuisance...but, also, there can be substantial kilocalories lost in the 
fecal matter, but more importantly loss of some components of fat that are 
essential to the functioning of the body (essential fatty acids).
     To counteract some of the food-related problems that will happen 
after a gastrectomy or stomach by-pass, recommendations include avoiding 
large meals (because of the small stomach capacity), drinking liquids in 
small amounts and not with meals, and being aware of the possible problem 
of lactose intolerance (from the sugar in milk...lactose...not being 
completely digested in the small intestine.  Also, the patient must be 
aware of the possiblity of long-term deficiencies of several B vitamins 
and may need supplements of several vitamins.
     I guess, if there is any good news to such a dismal set of 
circumstances, it is that people really do lose a substantial amount of 
weight after the by-pass, usually by about 2 years...but, some regain some 
of the weight lost.  Undoubtedly, the operation has saved some people's 
lives or has vastly improved the quality of the formerly-obese person's 
life.