Skilled DS surgeons almost routinely do the whole DS in one OP on very heavy patients. I met a patient in my surgeon's office who was over 800lbs on his surgery date. The whole 2 OP thing came about when 1 surgeon started pushing it. And writing papers. It meant more money for the surgeons and a lower skill level. Occasionally the 2 OP thing is valid. But usually it's an indication of the surgeon's skill level.

DS has two parts, a sleeve gastrectomy (partial stomach removal) and also a diversion of how food goes through the intestines.
Part 1: The gastrectomy part involves removing the curved side of the stomach, leaving a stomach that is shaped like a tube holding between 1 cup and 1 1/2 cups. (It was described to me as banana-shaped but now they compare it to a sleeve, but I guess it's the size of a toddler's sleeve!). The gastrectomy part of DS preserves the "pylorus", the natural opening of the stomach that regulates the flow of food into the intestines.
Part 2: the DS surgeon creates a "diversion" in the small intestine. The diversion separates the small intestine into two smaller "limbs", one for the food and the other from the pancreatic digestive enzymes and bile (that's the reason"biliopancreatic diversion" is in the name of BPD-DS). The diversion changes the usual way food is digested. The reason it is called duodenal switch is that the diversion starts at the duodenum, the first part of the small intestine.
Why it works: With DS, two thirds or more of the intestine is bypassed, leaving only a few feet of intestine where food and digestive enzymes meet. The "common channel" is the length of the intestine after reconnection, when food and digestive juices are brought back together. My common channel is 100cm, about 3 ft.
By keeping food separate from bile and digestive enzymes for all but a small section, the DS significantly reduces the intestinal area available for digestion of food and particularly fat (so a lot of calories go through without digestion), but it also gives less access for vitamin and mineral absorption. Darn it, but sugar and carb calories are the best absorbed!
At 13.5 years out, I am sure my stomach has stretched a bit and the intestines are getting more adept at digesting food, but I still weigh almost exactly half of what I weighed on my surgery day.

You touched a sore spit with me about Dr Now. DS is the most effective procedure for anyone who weighs 300 pounds, let alone 600 pounds. It is unconscionable that he continues to do a less effective procedure for these people. DS is a long and difficult surgery that isn't easy to learn, and maybe he can't or isn't willing to learn it. I won'****ch the show because I end up yelling at the TV and I can't endure the public humiliation and fat shaming that is part of the show.

Hi I don't have the DS, I have the sleeve. But I have diarrhea more than I have solid..I am almost 4 months post op and I have no hope it will get better. It's just my new normal. Also I have found that when I am extremely low with my carbs..like under 20 a day. My BM's are horrific in smell...I have come to the conclusion that the reason for the diarrhea is most likely because of the extremely low carb intake as well. About the only time I don't seem to have completely liquid BM's are when ease up on my limiting of carbs. I realize though that people with DS usually get diarrhea when they eat too many carbs or sugar though. Good luck!

Are you seeing a Bariatric surgeon? I was having the same problem but not losing weight however I was having diarreaha, sick at my stomach and could only eat a few things, my iron was low. Basically I felt very ill for months! I saw a Bariatric surgeon who diagnosed me with Candy Cane syndrome. He operated and fixed the candy cane and fixed my stomach which he said was basically a mess. I cannot tell you how much better I feel. No more tummy issues!! And no more bowel problems!! See a Bariatric surgeon!

I am 10 yrs post RNY, and have used psyllium husk 3 times a day to bulk up my stool. I'm not losing weight, but thought I'd offer what I had to do to stop loose stool and diarrhea