Prebiotics are compounds that feed your gut bacteria. When consuming prebiotics, our gut bacteria produce short chain fatty acids. These short chain fatty acids can help repair leaky gut, and many have claimed they may aid in weight loss. However, in biology things aren’t usually this simple. Let’s discuss how prebiotics can actually decrease short chain fatty acids in those who are overweight and how much weight loss prebiotic supplementation can yield.
Dr. Michael Ruscio: Hi, this is Dr. Ruscio. And let’s discuss if prebiotics can help with weight loss.
Now, what are prebiotics first? Prebiotics are compounds that feed our intestinal bacteria. So they’re food for probiotics, you could almost say. So they feed the bacteria in our gut.
And one of the reasons prebiotics are attractive is because prebiotics help to feed the gut bacteria, which then produce these compounds known as short chain fatty acids. And short chain fatty acids can be anti-inflammatory and help to repair your gut, your gut lining. So theoretically, there’s a lot of appeal in trying to increase the production of short chain fatty acids.
But it’s important, especially as a healthcare consumer, to realize that just because something can be good when we look at it under a microscope doesn’t necessarily mean that an intervention that facilitates that compound is going to be helpful in a human. And short chain fatty acids and prebiotics actually illustrate what I think is an important example of that.
Now, interestingly, in obese subjects—in people who are significantly overweight—oftentimes high levels of short chain fatty acids are reported. So that would be a little bit counterintuitive, where you would think that high levels of this compound would be good. Again, illustrating a concept that just because something is shown to be beneficial in a sense doesn’t mean that more and more and more of that compound is better. So more is clearly not better. Being in your physiological sweet spot zone is oftentimes the best spot to be in.
So this connects us to a current study—and I’ll put the abstract up here on the screen—that essentially took a group of obese subjects and gave them prebiotics. And they actually saw the levels of short chain fatty acids decrease.
So this is very counterintuitive. You would think short chain fatty acids are fed by prebiotics. So how is it that when we give obese subjects prebiotics, the short chain fatty acids don’t go up? They actually go down.
Well, perhaps what’s happening here is the prebiotics are feeding good bacteria. And as the good bacteria grow more, they’re policing out and crowding out some bad bacteria or some imbalanced bacteria. And when all these changes occur, the colony in the gut becomes more balanced. And therefore, we see more appropriate levels of short chain fatty acids.
So it’s not just about always trying to increase the levels. Sometimes, we have to decrease the levels. And to think about this more globally—just because something is good in a small amount doesn’t mean more is better, more is better, more is better.
So in this case, prebiotics were given to obese subjects. And their short chain fatty acids, which are anti-inflammatory but also high in obese subjects, came down, even though prebiotics feed short chain fatty acids.
So when we zoom way out, what does this really translate to in terms of effect? Well, the insulin levels in these obese subjects who received the prebiotic supplementation improved. Now, if we look at this, it’d be very simple to conclude that perhaps prebiotics would be healthy for weight loss.
Even more so, if you get roped into thinking mechanistically that prebiotics help increase, in some cases, short chain fatty acids, and short chain fatty acids are healthy for the gut, and I’ve heard that leaky gut can cause weight gain, then prebiotics can probably help with my weight gain through repairing the gut.
That theory is attractive. But when we look at the clinical trials with prebiotic supplementation for weight loss, the best results that we see are about 2.3 pounds of weight loss. And this is in overweight subjects. So that’s something. But the effect size is fairly small.
And so the reason I make this cautious commentary is because with the interest in the gut—which is great, because I definitely believe the importance of the gut deserves attention. But you have to be careful because you’ll be bombarded with all these different media claims about the next weight loss cure or the next leaky gut miracle or what have you.
And it’s just important that we contextualize that while prebiotics can do some interesting things, it doesn’t appear that they cause a major or significant impact on your weight, again, remembering that the best trial, at least to date, using prebiotics has shown about 2.3 pounds of weight loss.
It’s also important to keep in mind that sometimes you may hear estimates of prebiotics being able to produce a significantly higher amount of weight loss than 2.3 pounds. However—and here’s where the devil is in the details—these are oftentimes in studies where people go on a prebiotic supplement, change their diet, and start an exercise program.
So if you say, “People lost 10 pounds when they went on a prebiotic” but you don’t mention that they also changed their diet and started exercising, then you can’t truthfully say that the prebiotic caused 10 pounds of weight loss.
So just a few important notes for you as a healthcare consumer to be aware of—well, yes, prebiotics may have a favorable impact on short chain fatty acids and how those can be helpful for the gut, it doesn’t necessarily mean that prebiotics are going to be hugely impactful for weight loss.
Certainly, something to have a time and a place, prebiotics that is. But be cautious if you’re getting roped into the thinking that prebiotics are going to have an appreciable effect on your weight loss.
Okay. This is Dr. Ruscio. And I hope this information helps you get healthy and get back to your life. Thanks!
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