The Weird Reason Why Gastric Bypass Really Works

I know, I know. You’ve searched “Why Does Gastric Bypass Work” and got all the medical websites up on your browser. The first one that comes up for me is from talking all about the mechanics of the surgery.

It’s the scientific stuff! But if that’s really WHY it works, then why do so many people who have gastric bypass fail to achieve their goal after surgery?

Because the mechanics of the surgery is NOT the “Why” behind how gastric bypass works!

It’s just the “How”. How do I know?

I have succeeded with reaching and maintaining my weight loss goals after my own gastric bypass surgery – 5 years ago! I’m outside the percentage that initially failed or long-term failed.

So, here’s what I know.

why does gastric bypass work
why does gastric bypass work


Gastric bypass works because it forces the patient to follow a strict set of behaviors for 9 to 18 months after surgery.

Successful gastric bypass patients understand that if they follow their plan, as it is laid out, they will lose weight.


If I were forced to follow Weight Watchers or Jenny Craig and remove all outside choice, I would have lost weight with them.

That’s not how those programs work. That is how gastric bypass works. And why we get the surgery. But the pouch is like the training wheels on a bike or the bumper rails for kids learning to bowl.

We’re not getting off course this time, unless we demand to, and eat through the tool. Or if we fail to learn the lesson the training wheels provide. Don’t mistake the “How” for the why does gastric bypass work.


Around 41% of patients will regain the weight at 10 years after surgery.

Did your mind just explode? I’m still picking up the pieces of mine.

This is from a study published in 2017 from the National Library of Medicine (Monaco-Ferreira DV, Leandro-Merhi VA. Weight Regain 10 Years After Roux-en-Y Gastric Bypass. Obes Surg. 2017 May;27(5):1137-1144. doi: 10.1007/s11695-016-2426-3. PMID: 27798793).

That’s better than the study published in 2008 that sited the statistics at 50%. So, Yay??

No. Not yay. I’ve read through the results and the method listed in the study. And though I’m no doctor, I’ve got knack for the science-y talk and statistics.

Basically, they don’t cause my eyes to gloss over the medical terms and numbers. So, let’s see if I can translate.


  • We Forgot What Hell Felt Like
    • This feels like it should be last, because it’s so dramatic. But that’s why it’s first. When we get so far out from surgery that our prison is this distant memory, we forget how awful it was. And we forget the promise we made to ourselves to get out. Did you keep a journal before surgery? Did you keep one after? If so, go read it right now and remember what it was like. Do not go back there without a fight! NEVER FORGET YOUR “WHY”.
  • Pregnancy
    • Situational, only applies to females, but still sucks. Take your birth control the whole 18 months after surgery. You need to learn how to lose weight during this time. Pregnancy needs to wait. And that’s AWFULLY PAINFUL for people, like me, who got the surgery so they COULD have kids. I know. Wait. Learn how to feed yourself and move your body.
  • Sugar & Carb Creep
    • Sugar and carbs are EVERYWHERE. And unless you’re fending them off constantly, they WILL creep back into your life. And so will the pounds. You can bring them back, but cut them out again ASAP once the scale starts going the wrong way or your clothes get too tight. Find the balance.
  • Thinking Malabsorption Is Your Friend
    • In my mind, malabsorption should keep me from gaining the weight even when I eat excess calories. WRONG! This study done in 2017 goes over how there is SOME (only 11%) malabsorption only of fats after RNY, not carbs or proteins. So, you think you can eat however much you want? Nope, nope, nopey, nope. You have to learn portion control. I mean, this really is actually GOOD news, if you think about it. It means we’re probably absorbing more nutrients than we thought, too.
  • Peer Pressure
    • The farther I get from surgery, the more I have to remind everyone around me that I had surgery. It’s so easy to forget, because you get into a “New Normal”. You learn how to eat again. And I have to constantly remind my husband that I can’t have “just one more bite”. There’s also this weird thing that happens when we try to escape the role of “The Fat One”. Some people just won’t let it go, and it’s hard to keep fighting.
  • We Stopped Moving
    • Having weight loss surgery does not give you a free pass for life from exercise. Think of it, instead, like weight loss surgery is the thing that will help you start moving, but you can’t stop. Get active! Have an active lifestyle. Then, you don’t have to worry as much about the sugar/carb creep.
  • Protein Shakes
    • I said it, and I can’t take it back, because I mean it. Protein shakes on their own are so, so, so bad for you if you’re out of the liquid phase after surgery. The only time anyone should be taking them IS IF YOU ARE TRYING TO GAIN WEIGHT or cannot get in enough protein because of jaw surgery or are pregnant or on a feeding tube. The only time I will ever suggest a protein powder is if it is going into a baked good or we are cooking with it. The reason behind this is that protein powder is not real food. It is the most processed thing on the planet that we put into our bodies. We need REAL protein, and we need it mixed in with fiber carbs, and a little bit of fats to get the most nutrition out of it.

Are They Misleading Us For Money?

I’m SHOOK that there are some gastric bypass patients whose surgeons REQUIRE their patients stock up on protein powder before they will do the surgery.

That’s a huge breach of ethics, and a major conflict of interest. Because they are getting a commission on it.

If your doctor is requiring this of you, ask them this question: “What’s the commission percentage?” and then go find a different doctor immediately.

They should know the answer to “Why does gastric bypass work” and know that the protein shakes they are peddling are going to get in the way! M

aybe this is the actual #1 reason why so many gastric bypass patients fail. I’m not sure. I’ve scoured the medical publications and there are no studies, but I will keep looking.

Maybe when I’m rich I can fund the research. But, for now, I have to make assumptions based on my own knowledge of nutrition and the real-life examples presented in my life – of which there are MANY.


  • Preoperative Body Mass Index (BMI)
    • How tall you were in relation to how wide you were before surgery
  • Percentage of excess weight loss
    • How much weight you lost overall during your 18 month honeymoon
  • Weight regain
    • Gaining weight back did not cause you to regain more weight on top of it
  • Gender
    • Being male or female or nonbinary did not cause you to regain
  • Age
    • Younger people actually regained more… so… (and I think this one is a huge clue for us)
  • Nutritional monitoring
    • I scoffed when I read this one – out loud. Because if I know anything about gastric bypass patients, it’s that we’re not going to be 100% honest on our food journals. I’m 5 years out, and can eat what I want minus a few things. So, I’m actually a bit skeptical on this one, to be completely honest, unless the patients were locked in a room and only given specific meals for a set amount of time – unlikely.
  • Iron Deficiency
    • I have low iron, so this was good to know. Iron levels don’t mean regain.

This may be a relief for some of us to know that these are not factors in regaining the weight. So, what is???

Let’s look at the same bullet points pulled from this study done in 2016 around the Predictors of Weight Regain in RNY patients. (Shantavasinkul PC, Omotosho P, Corsino L, Portenier D, Torquati A. Predictors of weight regain in patients who underwent Roux-en-Y gastric bypass surgery. Surg Obes Relat Dis. 2016 Nov;12(9):1640-1645. doi: 10.1016/j.soard.2016.08.028. Epub 2016 Aug 21. PMID: 27989521.)


  • Not having a co-morbidity
    • The study found that those with a secondary health issue that is managed better by keeping the weight off did not regain as much as those who didn’t have this prodding them along. There’s not ANOTHER incentive to maintaining weight loss, like managing type 2 diabetes). Having diabetes or hypertension will actually KEEP the weight off. Mind blown, again. They aren’t making you regain, even though they aren’t on the list above.
  • Having the surgery earlier in life
    • Younger patients regained more weight. This one actually makes a LOT of sense to me. These patients experienced the awfulness of obesity for less amount of time. And another big factor I think that actually plays a bigger role as time goes on and we’ll eventually see as stats one day: fat positivity or health at every size movements. Damaging, damaging, damaging. Peer pressure plays a HUGE roll in every aspect of our lives, let’s stop pretending it doesn’t.
  • Length of Time Since Surgery
    • This one is kind of dependent on the other factors listed, so I’m a little surprised and very disappointed to see it as the conclusion. Basically, they say you’ll just regain as time goes on. I DO NOT ACCEPT THIS! F*** this answer. Let’s do better than that, scientists. These aren’t numbers, these are people.


Remember why you got the surgery, and the answer to why does gastric bypass work.

Go back to that place where you were miserable, and wanted out. Use that motivation to find the sugar and carbs and kick them out.

Gently remind your friends and family that you had gastric bypass surgery once upon a time, and that it still applies to your life today.

Move your body, get active and stay active. Stop living someone else’s life through TV, books, and other media outlets.

Drop the protein shake, and find the real proteins in your favorite meals and eat those.

Go check out the recipes section of this blog, and start cooking to really find out why does gastric bypass work!


Happy Weight Loss


For most of my life I was overweight. In my 30s, I became morbidly obese, tipping the scales over 330 pounds. After trying and failing at every diet, I decided to get gastric bypass RNY weight loss surgery. Since 2016 I have been living a much healthier life, I hit my weight loss goals, but more importantly, understand weight loss now. I am determined to share what I now know.

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