Aidan:
Hello, and welcome to the Ideal Nutrition podcast. My name is Aidan Muir, and I’m here with my co-host, Leah Higl. And this is episode 181, where we’re going to be answering the question of whether PCOS reduces basal metabolic rate. And this has come up for a few reasons. One is that women with PCOS traditionally have always found it more difficult to lose weight. So that’s one of the things that would raise the question about being like, is this one of the reasons why?
There also has been some research suggesting that BMR might be lower, which we will talk about as well. And the thing that honestly tipped me over the edge of wanting to do a full podcast slash deep dive on it is I’m gonna give credit to MacroFactor, who did a real deep dive on this topic. And I’d been coming to a similar conclusion over the years, and they just summarised it so nicely in one place. So that’s what’s prompted this podcast, but it’s a deep topic that I think is well worth talking about in general.
Leah:
Yeah. So, starting off with the evidence supporting a potential reduction in basal metabolic rate in people with PCOS. So there is a 2009 study from Georgopoulos, which I had to get a correct pronunciation of. Georgopoulos et al. is the most frequently cited study when it comes to this specific topic. And we’ll talk about kind of how that plays a part in the totality of the research after.
But basically, if you Google PCOS and BMR and you read all of the top posts, like this study is just referenced so much in so many different articles. So it’s very much contributed to this discussion and this particular space. So, in this study, women with PCOS but no insulin resistance were found to have a BMR that was 13% lower than women without PCOS. And then women with both PCOS and insulin resistance were found to have a BMR that was nearly 40% lower than women without PCOS.
So obviously that is a huge discrepancy. Like if that was something that was accurate, it would basically feel like you have perpetually dieting with like a 40% calorie deficit, which is huge just to maintain your weight. So again, like if this was something that we were seeing in the totality of the research, that would be enormous.
Aidan:
Yeah. And in terms of my own personal evolution from studying dietetics through to now, I’ve had a big evolution in terms of how I think about PCOS in this topic. One of the formative things for me was when I saw a TED talk from a certain evidence-based creator who mentioned that study. And I’m pretty sure only that study in relation to VMR, which made me think about it because I was like, I’ve never seen any research on that. Was very new to the journey, and I was like, okay, that’s interesting. I’ll keep that in mind.
I then wrote a blog post on the topic, which was number one on Google for ages, which I was super proud of. But I was doing a general blog post on PCOS, but then I spoke about that article as well. And that was a bit of a section in why it might be harder to lose weight. And then that evolved to being open-minded, being like, hey, we’ve got like one study here and then three studies over here that show that there’s no difference in basal metabolic rate. I’m gonna be open-minded.
And I think when we recorded a podcast, when we did one on PCOS, I was kind of talking about through that lens about being like, I’m open-minded to the potential that BMR is reduced, but there’s also a solid chance that it’s not as well. And now in 2024, and also acknowledging that there was also a few studies that I missed when I said there was a few over here. There’s actually, there’s a decent amount. In 2024, we have what I’d consider to be 14 relevant studies where seven quite literally measured BMR in women with PCOS versus those without. And another seven just measured it in women with PCOS. And when you really think about it, we don’t really need the comparison without because we have heaps of data on those without PCOS. So that individual study doesn’t actually need to do the comparison, but I thought it’d make the delineation there. But that therefore means we’ve got 14 kind of measuring it.
So, we now have 14 studies that are relevant. Thirteen of them have no difference. One has a difference. Going back to that macro factor article, you can literally go through and actually see the differences because I’m obviously simplifying when I say no difference. Like if you read the differences, you’ll find one that might have like a plus 50 calorie difference or a minus 50 calorie difference, but on average, no difference. So it’s pretty clear that there is no difference in them are from what we can kind of interpret from that, which makes us wonder, like, what happened to that 13th study or that 14th study? What happened there?
Leah:
Yeah, like, what happened there? I mean, like from a simple perspective, we could just say that look, there are 13 studies on a topic that show one thing. And then there’s just one study that shows a completely different thing. And whenever we’re looking at research, like obviously, we’re going to go with what is the kind of general trend. And it’s pretty clear that there is the general trend that there is no significant difference in BMR with PCOS versus without. And then I think getting into the explanation of why there could be a difference in this one study, I mean, it could just simply be a difference of equipment in that the equipment used to measure BMR in this outlier study was less than ideal.
Like the specific machine used doesn’t have validity data. So we can’t even really check that. But a higher-end machine from the same company has evidence of low accuracy. So, like literally a higher-end machine from the exact same company. And we do know that about it. So there are a bunch of reasons to be skeptical about that particular study and the results of it. Like even other research from the same group looking at women found somebody with an apparent BMR of 328 calories per day, which is just like absurdly low. And then, on the flip side, they also found someone with a supposed BMR of 4,000 calories per day, which, again, is absurdly high. So we know that there are these kind of major outliers and like how much did that play a role in the actual results of this outlier study?
Aidan:
Yeah, that’s crazy that 328 in 4000.
Leah:
Yeah, that’s huge.
Aidan:
Yeah. There’s a lot of things we’ve researched that we can, I don’t want to say, take for granted, but we just assume that something measuring resting metabolic rate is typically going to be accurate. And in many cases, it is. But then you look at individual data like that, and you’re like, we might as well not pay attention to that specific study in general. And in this case, that just happened to be from that same group, but it makes the question a lot of the data that they put out in general. And the big thing I come back to that is relevant for a lot of topics is, in this case, I’m like, if this one study never existed, would we think about this topic entirely differently? And I think it’s safe to say that we would.
If we had 13 studies just showing one thing without this study existing that, you can kind of explain why it is a bit of an outlier. We wouldn’t even be thinking about the topic. It would just be like, okay, I guess there’s no difference. And there’s no point doing more research after we’ve got 13 straight studies showing this thing, which leads to the next obvious question, which is a question I’ve gotten quite a bit from people: why is weight loss harder for women with PCOS?
We know that it’s clear that basal metabolic rate is not the explanation. That doesn’t mean that a woman with PCOS can’t have a lower basal metabolic rate. That just means, on average, there’s not a lower one. Just the same as somebody without PCOS could have a lower basal metabolic rate as well. So let’s just chucking that out there. But the first explanation is probably not the best explanation I want to go with, but I’m going to chuck it in there, too, because it’s relevant for everybody. Losing weight and maintaining weight loss is a hard thing in general.
We know, statistically speaking, across the board is a hard thing to do. If you felt like you were in a category where it was hard to lose weight and then you also had a hard time losing weight, you might link the two when it might just be hard in general. That’s not actually my main message. It is something that I do want to chuck in there as a small portion of an explanation. Let’s talk about the real message that I do have.
PCOS can increase appetite and cravings in certain cases, which obviously has a big role, that’s huge. The hormonal part of the condition can influence that. That is a very real and very valid thing that is contributing to this overall. I’m gonna touch on this insulin resistance. So, insulin resistance is often, but not always, higher in PCOS. Even stemming back to that study that we did talk about earlier, where like they linked lower BMI with higher insulin resistance. Insulin resistance is a common factor with PCOS.
But, research looking at other scenarios doesn’t find any link between insulin resistance and more difficulty losing body fat when calories are matched. For example, if we look at type 2 diabetes, we don’t see that. And type 2 diabetes, there’s often a lot of insulin resistance involved. The only reason I’m touching on that, even with the opinion that it’s unlikely to be a factor, is just because if I didn’t touch on that, people might think I’m negligent and avoiding a very important topic, whereas I just don’t think that that’s the explanation. I think the hormonal aspect and the changes in cravings and stuff like that are far more important.
And then another huge variable that plays a role. Statistically, women with PCOS have a much higher risk of both mental health disorders and binge eating disorders. Like if you look at the stats, it is actually a big difference. That very much would play a role. So the key message overall that I’ve got is weight loss is hard in general. BMR is not the reason that it’s harder on average to lose weight with PCOS, but there are many other reasons as well that are worth factoring into.
Leah:
Yeah, so overall it’s clear that basal metabolic rate is not affected on average by PCOS, but there are still many challenges faced by people with PCOS that can make weight loss more challenging. And I think that’s really the take-home message here.
Aidan:
This has been episode 181 of the I Do Nutrition podcast. As always, if you have not left a rating review, we would absolutely appreciate it if you could, mainly if it’s a positive.