There is a lot of misinformation around the menstrual cycle and how it impacts our metabolic health. This is one of my favorite topics and even the premise of my dissertation!

It is thought that insulin sensitivity goes down in the luteal phase when progesterone is high, and that we tend to use more fat for fuel.

However studies have been mixed with only one study from 2010 (yung et al.) showed here looking at long term or full cycle effects. Till MacGregor et al 2021 (shown here).

The current message in social media is that because “insulin is high and glucose changes we shouldn’t do high intensity exercise” at specific times of our cycle. But this is silly due to the benefits exercise has on metabolic outcomes!

Here we DO see fluctuations across the month. Glucose does appear to change with the cycle with small but possibly meaningful changes in insulin.

The new thing that the study here tells us is that while these changes may/may not be present — weight status, total weekly activity (500 Mets was their cut off for high), or cardiovascular fitness (assessed by VO2) all influence this!

The data is hard to see here but wanted to share for those who are visual. Pinch to zoom in. You can see 1) how these patterns change and 2) how much individual variability (how tall the bars are) there is!

*Disclaimer: the study here used BMI as a classification category. This is common in large data sets. I understand peoples frustration with this measure but am reporting a study “as is”.

& this matches a lot of the data we have on metabolic flexibility suggesting adipose status, daily activity, training level along side generic factors influence these metrics.

Now if you do not want to peruse intentional weight loss that is okay! My behavior change bias leans heavily toward the activity factors influence and if you zoom in here can see in the green line for highly trained HOMAIR is much lower in the luteal phases.

& mostly for those here who are active or had lower weight status or in general while there were fluctuations here many were still within normal healthy ranges!