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Uncategorized, weight loss

FDA approves vagal nerve stimulator for weight loss but does it work?

The Food and Drug Administration (FDA) just approved a new surgical therapy for weight loss called VBLOC®, essentially a pacemaker for the vagal nerve.

The vagal nerve has an intricate role in many bodily functions.  Among its duties is involvement in satiety (feeling full). Cutting the vagal nerve has been used for refractory epilepsy and along the way researchers found that some of those patients lost weight. VBLOC® offers a reversible version of that therapy – when turned on the pacemaker interrupts signals from the vagal nerve in the abdomen preventing transmission to the brain. It has a remote control so it can be turned on and off at will.

The device was approved based on one study published in JAMA in 2014. It was a double blinded sham surgery controlled trial, meaning everyone got the implant, but it wasn’t turned on for everyone. This is a great type of study because it truly allows you to see placebo effect. The active group lost 8.5% more weight than the control group.

My issue with the device is how significant is this weight loss clinically? While the actual cost isn’t known yet because the device isn’t on the market it will likely be in the $20,000 range for implant + surgery. That’s what most implants seem to cost when you add it all up. I use very similar technology when I implant sacral nerve stimulators, so I’m very familiar with implant technology, the mechanics of implanting, costs and the risks.

I suppose how well it works depends on your perspective and how you manipulate the statistics. While the 8.5% weight loss was statistically significant what does that mean in real life? Among the people who had the device turned on 52.5% lost at least 20% of their excess weight (not their body weight, their excess weight) and 38% lost at least 25% of their excess weight. Excess body weight was defined as the amount of weight that needed to be lost to get to a BMI of 25. Long term maintenance was not addressed as most of the data was 12 months of follow-up.

Let’s pick a patient with a hypothetical 100 lbs to lose (most people who have a BMI of 40 or more and thus candidates for the device have approximately that much weight to lose). With VBLOC® this patient has approximately a 50% chance she will not lose more than 20 lbs and a 62% chance she will NOT lose more than 25 lbs. 

The study has a lot of issues. First of all picking “excess weight” is an interesting metric because doesn’t seem to be what is reported for gastric bypass or intensive medical therapy trials, those studies seem to focus on percentage of total body weight lost and/or BMI.  For example with gastric bypass at 3 years the average weight loss is 21-25% from baseline body weight. Losing 20% of your total body weight is clearly better than losing 20% of your excess body weight. With VBLOC® the average amount of total weight loss was 9.2%.

Some people did have more dramatic weight loss, but not that many. 15% with VBLOC® lost 50% or more of their excess weight. But again, if you have 100 lbs to lose and you get the implant you only have a 15% chance that you will lose 50 lbs or more.

One thing I found interesting is that the study did not meet the main outcome measures, specifically the investigators were hoping that 55% would lose 20% of their excess weight and 45% would lose 25% of their excess weight. Despite that the device was approved.

The FDA standards for approval for many devices seem pretty low (something that has always confused me as a medication can be stopped but a device typically needs surgery for removal). Vagal nerve stimulators have been around for a long time for refractory epilepsy so the company simply had to prove there were no major issues with the implant and that it has some kind of benefit.

I appreciate that obesity is a major health problem and for many people who are severely obese surgical therapies work better than intense medical management.  Even losing 7% of your weight if you have a BMI of 40 can have health benefits. However, it’s hard for me to see that a device with an upfront cost of $20,000 (never mind the cost of on going maintenance) that helps only 38% of people lose 25% of more of excess body weight with 12 months of follow up is the answer. 

Is $20,000 for a 50% chance of a modestly successful surgical outcome, i.e. a weight loss of 20% (or more) of excess body weight, where we should be investing our money when it comes to obesity control?  

I’m not sure I have the answers and longer follow up may tell us more, for example effect on diabetes. If weight loss continues it’s possible by 3 years there may be more dramatic results with this therapy. So I’m all for more research with the device, however in my opinion by approving this device with the little amount of data available the FDA is setting the bar pretty low for weight loss surgeries. I imagine two check box on an FDA form 1) likely to maim/kill? Yes/No and 2) might possibly work Yes/No. If you answer No-Yes then you’re good to go as long as you have 12 months of data on a couple of hundred people. The public (and clearly investors) look at the FDA’s approval differently, they don’t see short study, few patients, 50% lose less than 20% excess weight, they just see “approval” so it must work.

We have a an obesity epidemic and whether VBLOC® will be part of the solution only time and more studies will tell.

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Discussion

2 thoughts on “FDA approves vagal nerve stimulator for weight loss but does it work?

  1. I’d love to see us investing the money that a VBLOC would cost in exercise classes and yoga classes for everyone! Let’s say every class cost $20. So you’ll have 1000 classes you can attend for free! Water aerobics or zumba with friends. Deep breathing relaxation techniques in yoga you can bring home and use for free. One surgery = 3 years of free daily classes. Or 21 years of free weekly classes. I’d enjoy that!

    Posted by koharjones | January 17, 2015, 7:58 pm
  2. I used TENS Unit against the pain of my knees. I must say that it helps me but only for a short period of time. I don’t know how often I must use it. Is it healthy to use it day by day or only twice a week? Thank you.

    Posted by Jennifer | December 29, 2015, 2:32 pm

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