Weight-Loss Surgery Myths Debunked – You’ll Miss Out on Key Nutrients

Posted on: 2nd Jul, 2021


In a new series, we’re debunking persistent myths of weight loss surgery. Read the first and second posts in our series, Weight-Loss Surgery Myths Debunked – You’ll Have Terrible Scars, and Weight-Loss Surgery Myths – You’ll Probably Gain Back the Weight.

The idea that you’ll miss out on key nutrients following weight-loss surgery isn’t true. But like every myth, underneath is a kernel of truth somewhere, so let us address it straight away. In the past, some kinds of more aggressive bypass-type procedures created vitamin and micronutrient deficiencies for some people. The worst offender, surgically-speaking, was the biliopancreatic diversion with duodenal switch, the old kind, and next up was long-limb gastric bypass. Today, neither of these procedures is done very often in the original way because decades ago, surgeons began modifying the procedures to eliminate loss of nutrients.  What’s more, neither of these procedures ever had much traction in the U.S. at all. Much milder micronutrient deficiencies can result from modern gastric bypass, especially if someone does not take their vitamins, but we’ll get to more on that in a bit.

Today, the most widely performed procedure is the sleeve gastrectomy, which has very little effect on reducing absorption of key nutrients. This is primarily because we absorb nearly all our nutrients in the small intestine, and sleeve gastrectomy never touches the small intestine. Making the stomach smaller probably does reduce some gastric cofactors needed to bind certain nutrients (like vitamin D and B12) so that they are later absorbed better in the small intestine. In this way, even the sleeve can exacerbate some mild nutrient deficiencies that are already present in the population.

The Question of Nutrient Loss

But there are three important reasons why the question of nutrient loss is not the primary question to be thinking about.

  1. It is all about overall health, not specifically certain vitamins. Look at giant countrywide studies or huge studies in the United States comparing weight-loss surgery patients versus traditional management of obesity, and you quickly find that after surgery, people live significantly healthier and longer lives. So, trying to identify the fraction of people who had to take extra vitamins totally misses the point, which is that, as a treatment, this procedure dramatically improves health and longevity. Think of it like this: if your sister had cancer and was considering a therapy that improved her health and added years to her life, what exactly is the point of finding that 20% of people experience a vitamin deficiency over the 10 years? Don’t we still want the best treatment for her? It seems like a good tradeoff.
  2. Missing out on micronutrients is not game over. It’s easy to take vitamin supplements and correct vitamin or micronutrient deficiencies. Metabolic surgery is highly effective, and the sleeve procedure produces minimal to no malabsorption of nutrients for the vast majority of people. Even a more aggressive revisional bypass procedure that does produce some malabsorption can be managed with vitamin supplements. It is a very small tradeoff for the improved health and longevity the surgery brings. Once again think of it like this: if your brother had a severely fractured hip and the best treatment was surgery, it makes no sense to throw up your hands and confine him to a wheelchair because he might not want to take a vitamin.
  3. The surgery is called “metabolic“ surgery because it changes the hormones and body chemistry, producing favorable events that are not reflected in nutrient absorption. The primary example of this phenomenon has to do with blood sugar regulation and diabetes. But it also occurs to some degree with blood pressure, triglycerides, polycystic ovarian disease, infertility, and obstructive sleep apnea. The changes from surgery in the body’s chemistry result in improvements of all these health conditions, even without losing pounds or changing nutrient absorption. I have too many examples each year to even list in which a patient who has had no vitamin troubles had little actual pounds lost, but still reversed their sleep apnea, type two diabetes, and hypertriglyceridemia. These things all result in improved quality of life, and improved health. Yes, we want more pounds off the body, but let us not forget there are additional benefits.


It is a myth that you will probably miss out on key nutrients, or feel worse, or look worse. The truth is you will probably take some vitamins, be healthier and more energetic, and maintain off a large and significant number of pounds for decades. And more importantly, you will enjoy improved health and a longer life. And by the way, if you were unlucky and had an unusually low vitamin level, it is correctable with a supplement. And that’s unlike the premature aging, fatigue, pain, diabetes, and early mortality of obesity, which is not so easily fixed without surgery.

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