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Why I Support Bariatric Surgery (Part 4)

In previous posts this week, I discussed the risk and potential benefits of bariatric surgery and explained why for someone with severe obesity and significant comorbidities, current evidence comes down heavily on the benefit side, whereas for someone with obesity but no complications, the risk/benefit ratio may not be all that positive.

In today’s post, I would like to look at why bariatric surgery works and hopefully dispel some common misconceptions about what bariatric surgery actually entails.

However, to fully understand why bariatric surgery should even be considered an option, we need to first understand why it is so difficult to lose weight and keep it off.

Readers will recall last week’s discussion on how any weight loss results in a ‘hypometabolic’ and orexogenic state – in short, weight loss drastically reduces the number of calories burnt while increasing hunger and appetite.

This is exactly what makes keeping weight off so difficult – as metabolism slows down and appetite increases, keeping weight off becomes a daily battle – a battle that lasts forever (the more weight you lose, the greater the struggle). This is why only a dedicated few, for whom weight management becomes nothing short of a daily obsession, manage to keep substantial amounts of weight off.

Everyone else, eventually gives in – most people can simply not endure constant restrictions or hunger forever.

Remember we are not talking about simply expecting someone who weighed 300 lbs to lose 50 lbs and from now on live on the same amount of food that a never-obese 250 lb person would normally eat.

No! To sustain the 50 lbs wieght loss, the formerly 300 lb person would need to perhaps survive on the amount of food that a never-obese 200 lb person would normally eat (or less!).

So expecting someone, who normally would have eaten 2500-3000 KCal a day (or more) to, from now on, survive on 1500 KCal a day or less, is a pretty hard sell – especially, as this person, thanks to the orexogenic response to weight loss, would be constantly hungry and thinking of food.

To make this kind of weight loss possible (even in the short-term), virtually all popular diets resort to certain ‘tricks’ to reduce hunger and increase satiety.

Increasing protein intake while drastically reducing carbs is one common variation (e.g. Atkins diet) – this approach takes advantage of both the satiating effect of protein and the anorexic effect of ketosis. This strategy, of course works fine as long as you can stick with it – but adding even a few more carbs or reducing the amount of protein immediately brings back the hunger and you fall off. Very few individuals manage to walk the fine line between hunger management and falling off – many simply get bored.

Another popular trick is to bulk up the food with lots of fruit, vegetables, or simply adding fibre supplements with plenty of fluids. The idea here is that these foods will expand in the stomach and hopefully fill it enough to create a sense of fullness despite eating fewer calories. This may well work for some people, but remember, the stomach is the size of a small football – it takes a lot of food to fill it.

Also, eating large quantities of fruits, vegetables, legumes, high-quality protein and complex carbs, rather unfortunately, given today’s nutritional landscape, is not only impractical, inconvenient, and expensive – it also requires a substantial time commitment and other changes in lifestyle (e.g. regular shopping for fresh ingredients and home cooking).

The third trick is to simply avoid high glycemic index (HGI) foods (especially refined sugars and other carbs), which (at least theoretically) reduces the ‘eat-crash-and-crave’ and ‘antilipolytic” response to the hyperinsulinemic surge that comes from ingesting readily digestible carbs. However, evidence that this is a viable long-term weight-loss or maintenance strategy, is rather limited.

So the bottom line is that sustaining weight loss with dietary restrictions alone requires both subtantial dedication and some clever and sometimes drastic modifications of your dietary intake to make it sustainable.

For the sake of brevity, I do not want to go into a discussion about the rather important role of exercise in all of this, as I am trying to get to the issue of how bariatric surgery works.

But before I get to the surgery bit, here is one last important piece of information regarding how these dietary strategies affect ingestive behaviour.

Most of the above dietary strategies focus on the homeostatic system, i.e. hunger and satiety. Only the Atkins diet, which also allows chocolate and other high-fat goodies as long as they are low in carbs, also caters to the hedonic system, i.e. appetite and reward – which is perhaps why some people find it somewhat easier to stick with.

So here in short is the problem that every obese person, trying to maintain a significant amount of weight faces: losing weight activates both the hemeostatic system (more hunger – less satiety) and the hedonic system (greater appetite, especially for highly palatable energy dense foods that are especially ‘rewarding’) – two systems that will eventually wear down even the most determined dieter.

This is where bariatric surgery can provide help.

In principle, there are two mechanisms by which bariatric surgery can work:

a) Reducing the size of the stomach or otherwise slowing the passage of food, thereby eliciting a stronger and longer-lasting feeling of satiety.

b) Bypassing a significant proportion of the gut to create maldigestion, which means that a proportion of the eaten calories will not be digested and absorbed.

These two principles are referred to as ‘restrictive’ and ‘maldigestive’ surgery, respectively.

Although this sounds simple enough (and variations of both principles have been around for over 50 years), the actual biology of how these operations really work is only now being understood.

Thus, contrary to popular belief, restrictive surgery (formerly referred to as ‘stomach-stapling’ or ‘vertical gastric banding’ (VGB) and its modern cousin, the adjustable gastric band (AGB)), does not work by simply making it difficult to eat.

If this was the case, you would see the same results from simply wiring your jaw.

The real reason restrictive surgery works is because it sends powerful neuronal and hormonal signals to the brain to create an early and strong sense of satiation, thereby reducing the need to eat large portions.

In other words, restrictive surgery tricks the brain into thinking that you have eaten a 12 ounce steak, when all you have eaten is 4 ounces. Suddenly, those tiny serving sizes shown to you by the dietitian is really all you need to feel completely full and satiated – portion control is no longer a problem. Wiring your jaw does not produce that sense of fullness but putting a band around the upper part of your stomach does – this is why banding works while jaw wiring does not.

A variation of this approach is the increasingly popular vertical sleeve gastrectomy (VSG), which essentially reduces the size of the stomach to that of a small banana. Once again, this operation works because, it no longer takes a 12 ounce steak to feel full.

In addition, VSG also removes a large part of the stomach that produces the hunger hormone ghrelin. This is why many patients with VSG no longer feel as hungry as before (some patients literally say that this is the first time in their life that they have never felt hungry).

Thus, VSG has two modes of action: it significantly reduces hunger while increasing satiation with smaller portions. Suddenly, eating less is no longer that difficult – imagine losing weight without being hungry and not having to eat huge portions to feel full anymore.

The mode of action of the ‘gold-standard’ Roux-en-Y Gastric Bypass (RGB) is even more complicated. Not only is the size of the stomach reduced (greater satiety), the remaining detached stomach secretes less ghrelin (less hunger) but the food also bypasses part of the gut, which affects food digestion and absorbtion (maldigestion).

But even this ‘triple whammy’ is not the full story. It turns out that the way in which this operation redirects food by bypassing the duodenum also has a profound effect on the secretion of gut hormones like GLP-1, which control insulin secretion and other metabolic responses.

In fact, experiments with devices that simply prevent this part of the gut from coming in contact with food (as in the endoluminal sleeve or ‘duodenal condom’), lead to an almost instant improvement in type 2 diabetes, even without any appreciable weight loss (although in the long-term, improvement in glycemic control generally tends to be proprtional to the degree weight lost). This mechanism of action is commonly referred to as the ‘foregut hypthesis’.

In addition, it may also be that this operation, by allowing more undigested food to rapidly enter the large intestine, leads to a release of gut hormones like PYY-36, which delivers a potent satiation signal to the hypothalamus. This effect is referred to as the ‘hindgut hypothesis’.

Thus, each of these bariatric operations, by different means, tricks the ‘starving’ brain into thinking that it is still getting all the calories it needs thereby ‘accommodating’ the hypometabolic response by allowing the ingestion (or absorbtion) of fewer calories, while at the same time ‘overriding’ the orexegenic response to weight loss.

This is what allows patients to survive on as little as 1400 KCal per day without feeling hungry – a feat that takes an almost inhuman amount of willpower to do otherwise.

So why do some people fail with surgery?

The short answer would be because surgery, primarily affects the homeostatic system (hunger and satiety) of ingestive behaviour and not so much the hedonic system (appetite and reward).

In other words, bariatric surgery deals well with the issue of ‘being hungry all the time’ and ‘never feeling full’ (especially after weight loss) but not so well with the issue of emotional eating or food-addiction.

The latter is not always true, because not being hungry and feeling full (not to say ‘stuffed’) also affects the hedonic system – but only indirectly – certainly not enough to fully stop emotional eating (see tomorrow’s post for more on this issue).

And of course, any form of surgery can be ‘sabotaged’ by not following the recommended diet – you can always still drink your calories or graze all day and and gain all the weight back – no bariatric surgery will stop that.

Fortunately, ‘self-sabotage’ is the exception and not the rule and needs to be dealt with in a very different manner – remember, the surgery is on your gut and not your brain.

So what exactly do patients have to do to ensure success of their surgery? Why is surgery anything but a quick or simple fix? And, what are the potential long-term complications of surgery?

More on this in coming posts.

Istanbul, Turkey


  1. Odd that grocery shopping and cooking plain food is impossiblly expensive and difficult, but bariatric surgery is not too expensive or too difficult.

    Weird world we live in.

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  2. Very informative post –
    complete with cliff-hanger at the end
    – I’ll tune in tomorrow …

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  3. It’s interesting that you mention maldigestion as a way to not absorb as many calories, while not mentioning that that same maldigestion also means one is going to absorb less of the nutrients in the food they eat – a lot less, as their portion sizes have gone from a normal 2500 -3000 calories a day to 1400 calories a day. The vitamin and mineral supplements necessary to replace what one is not getting from one’s food are not inexpensive either. So you’ve traded one expense, fresh fruits/vegetables, for another, higher expense, vitamin and mineral supplements.
    This isn’t even accounting for what happens to an altered digestive system when you send food through it. Before my VBG, I ate fresh fruits, vegetables, salads, and dairy products with no problems (I had to stay away from anything greasy, no gallbladder). TMI Warning – After my VBG, if I eat any of those items I listed and am not within close range of a bathroom, I will be totally embarrassed and humiliated by my body’s reaction to those foods. Explosive diarrhea is putting it mildly, to say the least. I’m basically limited to eating meat, eggs, cheese, potatoes, rice, and bread. Nothing greasy, no butter or margarine, no cottage cheese or sour cream or milk. Anything else and I’m hoping I make it to the bathroom before I have an embarrassing accident. I’ve talked to numerous doctors about it, and they say there’s nothing to be done about it, that reversing my VBG won’t change anything, and after almost 14 years, I doubt that it can be reversed. I’m not the only WLS survivor who has a problem like this, either, and is still super-morbidly obese after the surgery.
    Oh, and your definition of a 300-lb person losing 50 lbs and no longer being obese, I’m supposing that 300-lb person was at least 6′ 4″ tall, because most people, at 250 lbs, are still obese. I was 5′ 9″ and weighed 205 lbs and was obese by BMI.

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  4. These posts are very educational. I’m learning a lot. Thank you.

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  5. Dr. Sharma,

    Over the past year, I have lost 141 lbs. and have kept it off with ONLY lifestyle changes, so I take exception to some things you have said in this post.

    First, “This is exactly what makes keeping weight off so difficult – as metabolism slows down and appetite increases, keeping weight off becomes a daily battle – a battle that lasts forever (the more weight you lose, the greater the struggle). This is why only a dedicated few, for whom weight management becomes nothing short of a daily obsession, manage to keep substantial amounts of weight off.”

    Weight management does not have to become an obsession, as you put it, you must come to the realization that this is how you have to eat and behave for the rest of your life. It’s not an obsession, it’s a lifestyle change. Once you realize and accept that, the rest is relatively easy – it’s just a matter of DOING it.

    Second, ” Also, eating large quantities of fruits, vegetables, legumes, high-quality protein and complex carbs, rather unfortunately, given today’s nutritional landscape, is not only impractical, inconvenient, and expensive – it also requires a substantial time commitment and other changes in lifestyle (e.g. regular shopping for fresh ingredients and home cooking).”

    Yes, Dr. Sharma, making radical lifestyle changes and eating healthy is a lot of work, and it’s expensive, but, in the end, the benefits FAR outweigh (pun intended) the perceived hardship – and it’s one heck of a lot better than the alternative. I certainly wouldn’t call it inconvenient. If convenience is the alternative, a lot of people are looking a very “convenient” death square in the eyes.

    And finally, “So expecting someone, who normally would have eaten 2500-3000 KCal a day (or more) to, from now on, survive on 1500 KCal a day or less, is a pretty hard sell – especially, as this person, thanks to the orexogenic response to weight loss, would be constantly hungry and thinking of food.

    I have consistently cut down my “intake” from 2500-3000 KCal a day or more, to between 1500 – 1700 KCal a day and RARELY feel hungry. The trick is to eat healthy, eat the “right” foods – foods that fill you up (Power Foods, if you will) and to RELIGIOUSLY eat three meals and at least two or more “snacks” a day. Also, eating at the same time each day, getting into a set “routine” that your body eventually recognizes, expects and accepts are KEY to making this type of a lifestyle change work over the long-term.

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  6. Yes Jim, I hear you, and I can assure you that if more people could do what you are doing, I’ll be the first to put our surgeons out of business. Unfortunately, you remain an extreme outlier – good for you – but not a recipe for most of our patients (believe me, I wish it was!)

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  7. @Jim.

    Jim good for you! Keep it up. Like Dr. Sharma stated that not everyone is able to achieve what you have done. Research is certainly showing that obesity is a multifaceted dis-ease. Lifestyle is certainly only one aspect that must be undertaken as well as calorie restriction.

    In the past I have lost 70+ pounds three times in my life only to put it on and return to my approximate weight of 285.

    I think if we could avoid surgery we would, but for some this may be the only alternative. I believe you are very sincere in your comments and I appreciate that and wish you continued success!

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  8. Yes, Jim’s an outlier (btw, congrats, J). But Dr Sharma, the group of people you deal with constantly ( the extremely obese) are, while not as rare as Jim, also outliers among the total population. I wonder if some of these findings are true of this group of outliers but not of the totla population.

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  9. Dr Sharma,
    I’m reading these posts and comments with interest. If I understand you correctly, you’re saying that over the long term, even changing the diet drastically won’t be enough, because the body will sabotage your efforts with hunger and become more efficient about extracting nutrients from the food it does eat.

    But I’m interested in the testimonial of someone like Jim, who says he’s done it by doing what popular wisdom says you’re supposed to do – eat at regular mealtimes, eat good quality food, watch portion sizes etc and doesn’t feel hungry. This is my own experience as well. How can these two things be reconciled? Are people like Jim outliers, or is it that it’s simply too early to make a judgement and that the bodies of people who have lost weight will fight back at some later point, rather than at the time the weight loss happens? And what about the magic five year mark that’s often bandied about, that suggests that if you can keep the change for five years, then you’ve pretty much cemented the change?


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  10. @Alexie,

    I’ll let you know if five years!! lol.



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  11. Make that “in” five years!!



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  12. Jim, I’m at 8 years of maintenance. Simply, Dr. Sharma is right.

    I compare weight loss with down-hill skiing. It is followed by a “coast” period. That’s where you are, and many people are at year one. (Save yourself some regret and DON’T ever say, “If I can do it anyone can,” and keep your pride in check.) Another metaphor is that this is your “honeymoon” period. There will come a point, however, if you’re normal, that your ghrelin will start to elevate. After this period (one study has shown) ghrelin will be elevated by about 24% throughout the day, every day. (With bariatric surgery patients it is suppressed by 73% throughout the day.) Moreover, your Leptin and Peptide YY3-36 will also be suppressed.

    I don’t call the sensation this hormone imbalance produces “hunger.” (I suspect that there are other hormones at play when we experience legitimate, stomach-growling “hunger.”) I talk about “eat” impulses or “eat now” impulses. They are real, compelling and can be mind-consuming. I think many regainers judge themselves harshly because they haven’t been given a vocabulary to describe this phenomenon. They have words like hunger and appetite that are inadequate. They feel they have personally failed when they regain, because they ate when they weren’t technically hungry, and yet they were compelled/impelled to eat.

    I consider myself a living experiment, n = 1. I would welcome you to the club, Jim. While you’re in the coast period, prepare to switch from downhill to cross-country skis. Rather than thinking of maintenance as an “obsession,” I find it more useful to think of it as a third- to half-time unpaid job that requires a PhD in personal body management, which starts with incredible self-knowledge. (If you lost weight on a program that did your “thinking” for you, you have some catching up to do.) You will need to find ways to balance precise amounts of foods that sate you (which may be different from what works for other maintainers) with adequate exercise — not so much to balance intake (the old eat less, move more mythology) as to trigger exerise’s own metabolic effects that cue you to remain leaner than you were. Good luck in your pursuits.

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  13. Debra or Dr Sharma or both,

    Do you know what makes the ghrelin begin to elevate? And after what period does this begin?

    If someone is eating the ‘right’ amount of calories for their body (using the Harris Benedict equation or whatever the most recent one is) and is exercising and doesn’t feel hunger or unsatiated, what triggers the process being discussed? And why doesn’t the body defend its fat stores at the time they’re being lost, rather than after the event? e.g. why does it allow the person to lose the weight in the first place. If the body can deploy hunger to protect fat, can extract more nutrients from food etc, then why doesn’t it do that during the weight loss period, rather than afterwards?

    I want to know about this because I’m maintaining a weight loss myself, so any info would be gratefully received.


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  14. Thank you so much, DebraSY, for those words of discouragement!! lol.



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  15. I’m doing what Jim is doing. I’m going a good bit slower than he is, but I’m still going. I have, for many years, pored through the research and sifted the pop science from the science and found ways to apply it to myself. My goal: to do this without surgery. I understand that obesity has changed the mechanics of my body, most likely for the rest of my life. I do not wish to further change the mechanics of my body permanently but in a different way to address what I know has been caused by lifestyle. As my career changed from a semi-physical one to a sedentary one, I gained. As I became busier and busier and less attentive to my intake: I gained. And while my path is going to be much longer than Jim’s and much longer than the bariatric surgery patient’s, I do believe that in the end (my end will come when I die) I will be healthier and will have experienced a greater quality to my life than if I’d either done nothing or had the surgery. As an aside: my sister had the surgery 6 years ago. She’s only now returned home after 8 months in the hospital from yet another ill-effect of the surgery (which was reversed after her first bowel dissection 4 years ago). All the scar tissue has caused abscesses to form at the lesions of the scar tissue. The abscesses occasionally burst causing enormous problems. This time the abscess was on the stomach and the burst destroyed part of the stomach and separated it from the esophagus. 7 months with the stomach and esophagus separated while clearing the infections from the abscesses all in hospital and she still cannot eat more than a few small swallows of soft food and a nurse comes twice a day to administer her tube feedings. Her anatomy is forever changed and her quality of life has dropped dramatically from when she was over 300 pounds to her current 130. If we look at only the numbers, the surgery was a success for her.

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  16. Wow. Very informative article. Wish I had this level of knowledge. My story is one of “lost it the natural way”, yep, 104 lbs. Took me a year. Maintained the loss for 5 years. Exercised 2 hours everyday. To the point of obsession. Ate little carbs, measured and weighed all foods, ate only 3 meals and one snack a day, never ate between meals, abstained from processed foods, white sugar and flour. Attended OA. Prayed, therapy, worked my steps. Then I became pregnant. I was nauseous 24/7. Told to drink gingerale and eat soda crackers. The weight PLIED ON. Then after weaning my daughter, had a nervous breakdown, placed on mood stabilizers, gained ANOTHER 150 lbs in 6 months! I lived in HELL. I yo-yo’d for years. After 13 years I decided that the ONLY FDA approved method to prevent me from dying from all of my co-morbidities was Rou-En-Y gastric bypass. My weight was 380 lbs on the day of my program weigh-in. After 18 months my goal weight was met. I was graced with a 240 lbs weight loss. I am amazed on a daily basis of the health I can now enjoy. I am a “newbie” with WLS(weight loss surgery). I’ve maintained the weight loss for 10 months so far. I follow the “rules” of WLS. There are many. I use “gentle” exercise instead of fanatic crazy behavior. I attend therapy. I follow my 12 step program “rules” from 20 years ago. I take it a “day at a time” and pray that I will be in the group of 80% success with a sustained 80% excess body weight loss. I want to see my grandchildren grown. One thing I learned, and it helps me stay mighty “humble” was my original belief of “I lost it on my own, and maintained it for 5 years” meant that I was successful. “Just for Today” I am graced with the tool I need to stop my overeating, compulsive behavior, and healthy eating. Reach out to those suffering for this horrible DISEASE. Stop being petty and pointing fingers. Stop staring. Stop bullying. Treat others as you want to be treated. I am alive today because of WLS. Godspeed.

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