Bariatric Surgery

I had a pretty poor opinion of weight loss surgery already, but Health At Every Size all but says any doctor recommending it should lose their license for malpractice.  That claim seems worth investigating.  Luckily, she cites her sources.

First, I feel it’s important to note that bariatric is medical Greek for “obesity related medicine.”  I’m already not thrilled with that because I think excess fat is a symptom of health problems, but rarely a health problem in and of itself.  “Bariatric surgery” is often sold as something that is fixing a problem, the way an appendectomy fixes appendicitis, but it is at best undoing the damage of something else that is making you fat.

That said, let’s start with the immediate death rate.  HAES quotes a study as reporting a 4.6% death rate within the year: what it doesn’t say is that that study was done on Medicare recipients, meaning they were older than 65 or disabled.    Moreover, the 4.6% number is based on death from any cause, not what would be expected above and beyond what is normal for patients’ age and health.  Controlling for age, sex, and likelihood they would have died anyway* the researchers found that surgery increased your risk of death in the 90 days after surgery by somewhere between 90% and 200% (=3 times as likely to die), depending on which demographic you were in.  Inexperienced surgeons make this worse (which they do not back out of their model).  This is not just the stress of surgery: that’s twice the death rate following coronary revascularization or hip replacement, neither of which are minor.

HAES cites another study, published in JAMA as reporting a 6.4% four-year death rate.  This study has a number of problems.  Its only control was matched for age- and sex- but not health status.  A lot of the deaths stem from heart disease, which could plausibly be caused by being fat or having been fat, which is not a case against weight loss surgery.  Worse, that was the death rate only among people considered “at risk” enough to justify four years of follow ups.  The article doesn’t explain what qualified someone as “at risk”, but rarely does that risk mean “at risk of living too long”.  HAES cites a blogger who cites the study as demonstrating a 250%-360% increase in mortality over four years, relative to age- and BMI- matched controls, but I don’t see that anywhere in the original paper.

Meanwhile, the American Society for Metabolic and Bariatric Surgery aka “the people doing the surgeries” is happy to report a mere 0.2%-0.5% mortality rate after the first month of gastric bypass surgery.

That’s everything the book cites on mortality, which I found unsatisfying, so I turned to Dr. Google.  This Swedish study actually bothered to match controls (although surgery was not assigned at random, introducing the possibility that the surgical patients varied on a factor they didn’t think of) and found a 30% reduction in death over 10 years.

But I hate it when people act like death is the only bad thing that could ever happen to you.  What about people who don’t die, but do suffer for the surgery?  HAES cites six studies showing long term nutritional deficiency.  Of the five I was able to find online, all showed serious deficencies and none had a control.  Interestingly they all found a vitamin D deficiency, when vitamin D is primarily produced by your skin in response to sunlight, unless you live in Seattle, in which case you mostly get it through supplements.  Either way, food is not a major source of it, and if bariatric surgery effects vitamin D levels (which these studies have not demonstrated) I am extremely curious as to why.  Given the current controversy as to the efficacy of vitamins even in people with normal stomachs, it’s not clear how much this issue could be fixed with supplementation.

Every study I’ve read agrees that people lose substantial weight after surgery and then gain some of it back, I’m not even bothering looking for citations for this.

CONCLUSION: bariatric surgery has severe risks.  These may be partially compensated for by a skilled surgeon and good nutritional technique.  For extremely obese patients the benefits may outweigh the risks.  We don’t know where the cut off is for “fat enough to benefit.”  The strongest piece of evidence against bariatric surgery is that no one has done the fairly obvious studies that would conclusively demonstrate their effectiveness.

Some of the benefits probably stem from societal approval rather than genuine health issues, and the long term fix for that is for society to stop shaming people for their weight.  Another part of the benefit may be a forcing function, i.e. if patients ate like they’d had the surgery they’d lose weight whether or not they actually had it.  For an individual living in the society they live in and who has already tried dietary changes, this is sad but irrelevant to the decision.

I’m really uncomfortable with this conclusion.  It doesn’t fit my prior model, and I prefer the tribal affiliation of strong weight loss surgery opponents to strong weight loss surgery advocates.  I consider the evidence I’m basing this on somewhat iffy,  but in all honesty if it had come out the way I expected I would be fine with it.  I’m also pretty disappointed in HAES for so blatantly misrepresenting the evidence.

*Risk of death was calculated using the  Charlson Comorbidity Index.   I have no idea if that is a good model, but it appears to be standard.  This doesn’t prevent the researchers from being wrong but it does mean they’re probably not being deliberately manipulative.