Background

Originally designed for patients with diabetes mellitus (Type 1 Diabetes), Continuous Glucose Monitoring (CGM) devices that measure blood glucose “continuously” and at fine intervals (usually every 1-5’) are rapidly proliferating to other consumer segments, especially athletes. CGM devices still require a prescription, but many new CGM startups (SuperSapiens, Nutrisense, Levels, etc.) offer this service as part of their subscription.

While there is a wealth of anecdata (i.e. anecdotal data) that suggests using a CGM may help identify changes that can result in improved athletic performance such as is highlighted in these Outside magazine articles here and here, it’s important to note that the link between blood glucose and performance is “complicated”. Currently, there aren’t any clinical studies that validate use of CGM for athletic performance, nor are there clear guidelines on how athletes should use a CGM for this purpose. However, studies & guidelines for new applications of existing technology can take time and I was very curious, as you may be, about the data and insights that could be gleaned so I opted to demo a CGM service and below are my learnings, insights and recommendations.

Using a CGM

You attach a CGM sensor containing a fine needle to the back of your arm & wear it continuously for 2 weeks at a time. The CGM device is easy to apply and painless, although mine was bulky so had my husband help me to ensure it was situated properly. To secure & protect the sensor, it’s best to wear a waterproof patch (either provided by the service or purchased online) to cover the CGM and ensure it stays attached & ensure it functions properly. I had some trouble here so best to have some extras on hand!

You use an app to check in your CGM monitor data regularly (usually every 6-8 hours) as the device has limited storage capacity. You will also be asked to keep a detailed log of your meals and activities to help identify triggers that result in different patterns in your blood glucose response. The service I used also provided composite scores to help interpret the blood glucose response for each tracked meal and included access to a registered dietician to help answer questions for the first 30 days and for a fee after the initial month.

Observations

It’s all about the tracking, tracking and more tracking: The quality and depth of the insights you can obtain from the CGM are directly related to the data you elect to track in the application so the more types of & granularity of the data you track, the more helpful it is interpreting your blood glucose response. So it’s best to be prepared to log specific details of your meals/beverages, activities/training, sleep & stress levels as each of these can have a significant impact on your blood glucose levels. Unfortunately, the app I used didn’t integrate with any other platforms (e.g. Whoop, Cronometer, Garmin, etc) so I found having to duplicate the tracking log redundant & a bit tedious but critically important for interpreting results and getting value from the CGM service and represents a significant opportunity for these companies to improve the user experience.

Be prepared for some surprises: As you’ve likely heard me say before, one size does not fit all and “conventional wisdom” may not necessarily apply to you. For example, I learned that a low glycemic index food spiked my blood sugar much more than a high glycemic index food despite my belief the opposite would be the case. The key strength of the CGM as it allows you to learn your unique responses to foods, training (and other stimulus) provided the data is tracked in the app.

RD support is important: There is a lot of data! The CGM is monitoring your blood glucose 24 hours a day every 1-5 minutes so it’s helpful to select a service that includes or offers the support of a registered dietician (RD) who can help you dive into the data to better understand & interpret your results and build experiments to test various influences. For example, I ate the same meals two days in a row and had vastly different blood sugar responses which was a headscratcher. With the help of an RD, I learned that disrupted sleep may impact blood sugar the following day which helped me explain this conundrum (note: I wasn’t tracking my sleep in the application at the time so the app couldn’t help me with this observation).

Have a plan to maximize your ROI: Using a CGM is not inexpensive and typically requires a large investment and/or subscription so it’s best to go in with a clear rationale for what you want to learn, why and by when. The service I used was $450 for one month and $350/ month with a 3-month commitment & cancellation fees on the 3-month subscription were hefty. So aside from a few interesting insights gleaned in the first month (see below), I didn’t find it worth my investment, especially when I had to duplicate all the daily tracking data as noted above. But then again, I didn’t go in with a clear plan/learning agenda with the questions I was hoping to answer (my focus was on evaluating the experience and the data provided). And as mentioned above, be sure your plan includes support from an RD to help you maximize learnings (especially those you haven’t considered upfront).

Nutrify Recommendations

Consistent with Nutrify’s guiding principles, our first priority is to ensure our athletes are eating enough, obtaining key macro & micronutrients, and are properly hydrated. Unfortunately, as highlighted in an earlier post, many athletes are just not eating enough which can also result in in macro & micronutrient deficiencies that impede performance and impact overall health.

So, unless there is a known blood glucose issue to be addressed (i.e. A1C is high), and without evidence based guidelines on how to best use a CGM to improve athletic performance, we recommend focusing first on a comprehensive nutrition assessment and invest in an InsideTracker biomarker panel to provide a clear and comprehensive baseline that can be used to develop a roadmap and set of priorities for the athlete seeking to improve performance. For those athletes that do learn in this process (or already know from other labs) that they have elevated fasting blood glucose or A1C, utilizing a CGM can add significant value in identifying specific drivers and actions to that help manage blood glucose to improve overall health, especially in partnership with a RD.

Interested in learning more about what is included in the Nutrify Nutrition Assessment and how InsideTracker biomarker testing may be beneficial for you? Schedule a complimentary 15’ call to learn more.