Continuous Glucose Monitoring: A Case Study
We’ll start this blog with a confession. It’s not one i’m proud of but it needs to be said. Recently, I found I had been influenced by a #SponsoredAthlete….
As some of you may have seen, Sam Briggs has been training with a small circular patch on her tricep. Turns out this patch is a blood glucose monitor, it is the same as those with diabetes use to track their insulin levels, only Sam is not diabetic, she’s simply an athlete trying to optimise all aspects of her game, including her blood glucose levels.
Glycemic Index And Glucose Monitoring
The thinking behind blood glucose monitoring from the team at super sapiens (those behind bringing it to the sporting world) is ultimately to actively see and track when we have high levels of blood glucose available to us in the blood. Theoretically, training at these times will be more effective than when we have low blood glucose.
However, lots of things affect these levels, and we already have some guidelines with regards to this. The guidelines I’m referring to from a nutrition standpoint are those of glycemic index.
The glycemic index of a food is essentially the amount by which it raises your blood glucose levels. High GI foods tend to be simple carbs as they’re digested quickly and thus spike your blood sugar, examples are white bread and rice. Low GI foods tend to be higher in fibre and thus are digested a little slower creating less of a spike in blood glucose. High GI foods are useful for quickly replenishing glycogen stores and providing quick hits of energy when needed. BUT low GI foods are often associated with better health and even weight loss.
Why Monitor Blood Glucose?
Sweet so if we have a measure of this, why bother monitoring it?! A fantastic question and one I’ll answer across the blog but first we’ll establish that there are some issues with the glycemic index.
One of these issues is that apart from certain situations, we rarely consume just one type of food or one type of carbohydrate. Even simple snacks like cereal bars contain a combination of simple sugars, lower glycemic index carbs, fats and some protein, thus the glycemic response from something like this is likely to be slightly different than expected.
That’s even before we bring in the fact that different humans will have different responses, this is something myself and my friend and fellow nutritionist Liam found as we both have carried out 14 days with super sapiens (more on that later). And the final issue is ultimately that things like exercise can again alter the blood glucose response! So sadly it isn't as simple as just going off glycemic index.
Now that’s not to say that everyone should use blood glucose monitoring, but it can be useful! Let’s dive into my story, things I found useful around training and day to day life, things I wasn’t a huge fan of and where it may have the most efficacy in sport.
Feedback
The most obvious finding I experienced across the two weeks was the fact that my insulin response to feeding seemed to be relatively large!
Different meals resulted in different spikes in blood sugar as expected, larger more carb based meals resulted in bigger spikes, smaller protein dense meals resulted in a more muted response.
BUT in all situations around 40-60 mins after eating my blood sugar seemed to come crashing down. It is of course normal for blood sugar to drop after a meal as insulin is released resulting in an uptake of blood glucose to store it as glycogen or for the cells to use.
However mine would plummet below the supposed target range of glucose. For context, supersapiens does offer certain “target ranges” for different circumstances. These are based off what we know in the literature to be “normal” values for blood glucose.
For example hyperglycemia is classed as when blood glucose levels are above 125mg/dL and hypoglycemia is classed as below around 65mg/dL. Post feeding my levels regularly dropped to 55mg/dL before jumping back up to around 80-90mg/dL (a more normal level). This even occurred with small pre workout feedings that I would normally have 45-60 mins prior to training hoping to ride the beautiful wave of a spike in blood sugar.
But if you’ve done the maths you may have figured out the opposite occurred. I would start training during supposed hypoglycemia.
Now training itself results in a change in blood glucose as the body makes muscle glycogen available for use so after the warmup I found my levels swiftly came back to normal but it was interesting to see and has made me consider pushing said snack back to around 90 mins prior for more level blood glucose.
An interesting find for sure! But in the grand scheme of things has not greatly impacted my training or performance. I am of course by no means an elite athlete though. Which does lead me on to the potential efficacy of BGM in those populations!
I work with several elite level CrossFit athletes, a few ultra endurance athletes and with a group of Motorsports and Esports athletes. Across these 3 groups, I believe that the one that would benefit the LEAST from BGM is the CrossFit athletes.
I still believe that a 14 day profile of how they respond to different feeds will come in very handy for planning fuelling throughout the day and for competitions, but it’s likely that they’d only need that profile and then they’re good to go with perhaps another profile while testing competition scenarios too.
Endurance Athletes
Now let’s talk about perhaps the most obvious group, the ultra-endurance athletes. This is a group of people where substrate availability is CRUCIAL. When you’re on the move for 5,6,7,8 hours a day, glucose availability is so important. The simplicity of supersapiens and the fact it gives you LIVE data can be very useful hear. Both in being proactive and planning tried and tested fuelling strategies to ensure you’re not having any hypo’s or “bonks” along with being reactive and able to change the plan if blood glucose levels start dropping in the race.
For this reason though, I believe it has now been banned in some disciplines! Certain cycling time trials won’t allow it for races, this is not to say you can’t use it beforehand and plan out a fuelling strat you know works but does give you less room to react on the day.
Esports
The 4th group I mentioned is esports athletes. Now this is a slightly different benefit, and more one of buy in to nutrition improving cognitive performance. Generally an esports athlete may train or compete for 6-12 hours/day. For the most part not a huge amount of thought goes into their diet, they simply eat what is available to them and quick and easy without interfering with the gaming.
Now, if they were able to see how this was affecting their blood glucose levels, and if we could translate any potential rebound hypos to drops in performance, then immediately you’re onto a winner.
Having objective data is often what's needed for behaviour change. You cannot improve what you don’t track and so bringing those together I believe can have some real efficacy!
Motorsports
It's something that i’ll potentially be considering using with my Motorsports athletes, the factors that affect performance in motorsports are similar to those in esports when we think about cognitive function. So monitoring and creating tailored fuelling plans designed to prevent Hypo’s that may affect reaction time and focus could be very useful.
Especially with the guys participating in 24 hour races! The info gained will then be something i’ll use to create tailored nutrition plans based on individual glucose responses to enhance endurance, focus, and overall performance, making blood glucose monitoring a valuable tool in this high-stakes environment.
The General Public
Now onto the general public and certain things that I was not a fan of throughout this little process (which is more a reflection of me than the product). When I first started tracking my blood glucose levels I almost found I could be “ruled” by them. I’d see a hypo and immediately start looking for something to bring it back down, post workout I’d be frantically dashing for carbs to almost “beat” the hypo I knew was coming.
This is similar in a way to how a whoop band can control you to an extent. I am personally NOT a fan of whoop, I see people wake up, feel fantastic, their whoop says they recovered terribly and immediately they feel terrible…The opposite is also true!
People refusing to take a day off as “I’m in the green” yeah but you can barely walk your doms are that bad. As I say, early days tracking blood glucose was very similar and did not like it as it did not reflect a huge change in my performance or recovery.
BUT as the 2 weeks went on, I almost relaxed into it, understood how the objective change in blood glucose married with my subjective feelings and could become more intuitive with it!
For example, I’d see a hypo, then assess if I was feeling any symptoms of hypoglycemia, if not, cool, it’ll return to normal. If so, then yeah maybe grab something as it seems needed!
After the 2 weeks I am able to unplug, using what I've learnt of myself both subjectively and objectively to better control my blood glucose levels and energy levels.
All in all, I enjoyed this little experiment and can see HUGE use in the technology for certain populations, I am likely not one of those population groups but I will be using it with my athletes across all disciplines I’ve mentioned here.
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