Anyway, I went on the hunt for some information. I had a hard time really finding anything concrete. I see message boards were people are asking and answering questions, but not much "real" authority. Here's some of what I found:
No one knows for sure; each person has their own experiences. However, since weight loss tends to slow for most around the 18 month mark, that is a safe benchmark I suppose.
Studies on this topic are mostly done on patients who had cancer or some other form of a diseased intestinal tract and had to have a portion of their intestines removed to save their lives. The body is pretty amazing and can "heal" itself to a certain extent. The micro-nutrient malabsorption (vitamins/minerals) will never fully repair, but the macro-nutrient (calories/protein/fat/carbs) malabsorption will eventually be repairs completely. This process is called adaptation.
From what I've read, it looks like the adaptation process begins almost immediately after surgery - within 4 days. But it can take up to 2 or 3 years to complete depending on your body and how much was bypassed. The remaining intestine will grow longer and stronger and more dense villi - the little finger-like tentacles that grab nutrients from food as it brushes by. It's also called the brush border. But since vitamins/minerals have assigned locations of absorption, no amount of extra villi will make us absorb vitamins that had their assigned location bypassed. Here's a diagram [note: link no longer valid] that explains those locations.
For more reading about Adaptation. Here's some links:
This doctor claims that there is no caloric malabsorption at all: http://www.thinnertimesforum.com/topic/59658-calories-in-normal-stomach-vs-gastric-bypass-stomach/?p=730692
Your food is absorbed by your small intestine. The stomach churns up your food, and the stomach juices start the digestive process. After a gastric bypass you will probably still absorb 100% of the calories that your eat. There is less absorption of B12 and Iron, possibly of Calcium, but unfortunately not of calories.
Web MD: "Gastric bypass
Gastric bypass surgery makes the stomach smaller and allows food to bypass part of the small intestine. You will feel full more quickly than when your stomach was its original size, which reduces the amount of food you eat and thus the calories consumed. Bypassing part of the intestine also results in fewer calories being absorbed. This leads to weight loss.
Medline Plus: "Your diet after gastric bypass surgeryURL of this page: http://www.nlm.nih.g...ions/000173.htm
You had gastric bypass surgery. This surgery made your stomach smaller by closing off most of your stomach with staples. It changed the way your body handles the food you eat. You will eat less food, and your body will not absorb all the calories from the food you eat.
Laproscopic MD: "This technique is called a roux-en-Y intestinal bypass. Once in place, food passes from the stomach pouch directly into the jejunum, bypassing the duodenum. Because of this bypass, there is reduced absorption of calories and nutrients.
ASMBS association says "Treatment of morbid obesity and obesity related disease and condition: limits the amount of food the stomach can hold and/or limits the amount of calories absorbed.
Any malabsorption from calories wouldn't last for long anyway.
The body is a miraculous thing and our intestines grow additional villi to compensate for the RYN's bypass. Villi are finger-like projections in the small intestine that help absorb food more efficiently in the body.
At a recent follow up I asked my doctor about villi regrowth and she said it doesn't happen. She also said if your tool stops working completely it's due to human error - not measuring or eating the appropriate foods, fluid intake, etc.
Patients who have had a part of their intestine removed by surgery undergo a process called intestinal adaptation. During intestinal adaptation, the intestine may grow in size after surgery. The surface area inside the intestine increases as the mucosa (lining of the intestine) becomes thicker. The villi (the lining of the intestine responsible for intestinal absorption) become longer and denser, helping to promote absorption of nutrients. The diameter of the intestine may also increase.
Here is a diagram from the posting above, which shows were things are absorbed.
So according to what I found, you may be malabsorptive for 12, 18 or 24 months, or not at all. Who knows...but I do know that whether I am absorbing my calories, I do have to be very careful with my vitamins. I still have my blood labs on a yearly basis and each year I am somewhat deficient in something. So I just "up" that vitamin and by the next year, I'm good.
Have you ever heard about calorie malabsorption? If you have links to articles, please post them!