Key Topics Covered
- Women with PCOS traditionally have found it more difficult to lose weight.
- Some evidence suggests that BMR might be lower, which we will discuss.
- MacroFactor did a deep dive into this, tying together a lot of research.
Evidence Supporting a reduction in BMR
- A 2009 study from Georgopoulos et al. is the most frequently cited study that compares the BMR of women with PCOS to those without.
- If you google PCOS and BMR and read all of the top posts that come up, almost all of them reference this study.
- So, it has contributed very much to the discussion on the topic.
- In that study, women with PCOS but no insulin resistance had BMRs about 13% lower than women without PCOS.
- While women with both PCOS and insulin resistance had BMRs nearly 40% lower than women without PCOS.
- Which is a huge discrepancy! If this was accurate, it would feel like having to perpetually “diet” with a 40% calorie deficit just to maintain your weight.
Evidence Against That Reduction in BMR
- That one study is pretty compelling, but there is more evidence.
- There are 14 relevant studies. You can find these by going to our show notes and looking at that MacroFactor article where they have arranged it nicely.
- 7 of them compared the BMR of women with PCOS to those without. The other 7 didn’t have the comparison, but still add to the body of research since we obviously have so much research on the BMR of women without PCOS.
- Basically 13 of the 14 found no major difference in BMR. That 14th was the one we mentioned earlier.
Interpretation of WHY That Outlier Exists
- So why does that outlier study exist? And how do we interpret the totality of the research on this topic?
- From a simple perspective, we could just say that if 13 studies on a topic show one thing and the other shows something different, it probably makes sense to focus on the 13
- One explanation for the difference could simply be that the equipment used to measure BMR was less than ideal in the outlier study.
- The specific machine used doesn’t have validity data, so we can’t even check that.
- But a higher-end machine from the same company has evidence of low accuracy.
- Overall, there are a bunch of reasons to be sceptical of the outcomes beyond that.
- Other research from the same group looking at women found somebody with an apparent BMR of 328 calories per day and somebody else with one that was almost 4000 calories per day. Both of those are absurd OUTLIERS.
If this ONE study never existed, the debate likely would never have existed in the first place, so it begs the question. Is it still worth debating without more research showing a discrepancy?
Other Reasons Weight Loss Could Be Hard
- It’s clear BMR isn’t the explanation for why weight loss with PCOS could be harder.
- Note: This doesn’t mean somebody with PCOS can’t have a lower metabolism. It just means that, on average, women with PCOS don’t have lower metabolisms.
- One first explanation that I want to start with before exploring other things is that weight loss can be hard in general. It’s not helpful, but it is a relevant starting point.
- Adding onto that, PCOS can increase appetite and cravings in certain cases, which has a big role. The hormonal part of the condition can influence this a lot.
- Insulin resistance is often (but not always) higher in PCOS. However, research looking at that in other scenarios doesn’t find that it plays a role in making weight loss harder. I’ve just added this because otherwise, people might point out that I’ve missed this – when it’s just not something that explains it.
- Statistically, women with PCOS have a much higher risk of both mental health disorders and binge eating disorders. These very much play a role.
Summary
Overall, It’s clear that BMR is not affected on average by PCOS. However, there are still many challenges faced by women with PCOS that can make weight loss more challenging.
Relevant Blogs/Research
Relevant blogs:
No, PCOS Doesn’t Lower BMR (Scientific Review) – MacroFactor
Nutrition for PCOS: Everything You Need to Know
Relevant Podcasts: