Two of Europe’s leading diabetes organizations have just released new guidance for people with type 1 diabetes (T1D) on how to use continuous glucose monitoring (CGM) for exercise. This is a big deal because while we know exercise is important for good health for everyone, it can also greatly increase the risk of dangerous hypoglycemia for people with T1D.
But now for the first time, we have professional medical advice on how to leverage CGM to safely up our game in the gym, on the track, or in the pool.
So what do they recommend and how does this advice stack up to previous recommendations?
Published in October of this year, the guidance comes to us from the European Association for the Study of Diabetes (EASD) and the International Society for Pediatric and Adolescent Diabetes (ISPAD). Never heard of them? You can think of EASD as being the European equivalent of the American Diabetes Association (ADA), a huge professional organization for doctors and researchers. ISPAD is much the same, but with a narrower focus on diabetes in people under age 25.
The leading American diabetes nonprofits JDRF and ADA have both backed the new guidance. Officially, JDRF “endorsed” the document, while the ADA “supports” it.
Glancing at the position statement’s summary, it looks simple: The sensor glucose target range for exercise should be between 126 mg/dL and 180 mg/dL. If you are at the bottom of that range and you’re currently exercising, you need to consume carbs.
This we all know, but what’s new is the integration of CGM trend info into the advice of how many carbs to consume. Recommendations for carb consumption are “stratified” based on the rate of change in glucose levels indicated on your CGM.
What they recommend is that during exercise, if you are at 126 mg/dL (a seemingly perfect glucose level):
- If your CGM shows a full down arrow, immediately consume 20 to 35 grams of carbs.
- If your CGM shows a quarter down arrow, immediately consume 15 to 25 grams of carbs.
- Even if you have a flat arrow, consume 10 to 15 grams of carbs. In other words, don’t wait for a drop, you’re at the bottom of the target range and you know you’re gonna go low because you are working out.
But it’s not really that simple. The guidance is more complex than it first appears, is data-dense, and is on the long side at 20 pages.
As you dig into the published paper, you’ll find the authors admit: “Because of the complexity of CGM and is
They also correctly recognize that “different groups of people with type 1 diabetes may require different glycemic ranges in preparation for, during, and after performing exercise when using CGM,” so they break their recommendations out for different groups of people with diabetes:
- By age: over 65, 18 to 65, and 6 to 18 (not enough data exists to provide recommendations for children under age 6)
- By hypoglycemia risk: high, moderate, or low
- By level of exercise: minimal, moderate, or intensive
The end result? Take, for example, the “Sensor Glucose Targets in Advance of Exercise” table for various types of adults. It looks like the engine start checklist for a 747 airliner.
And it doesn’t stop there. There are six footnotes at the bottom of the table. My mind glazed over just looking at it. The same is true for the “During Exercise” and the “Post-exercise” tables. And then there are tables for children and adolescents as well.
It’s a lot of information.
Turns out there are no cut-and-dry recommendations here. Everything is relative based on the three parameters of age, hypo risk, and level of exercise.
Even that 126 mg/dL target mentioned in the CGM Arrows section above turns out to be a moving target.
It’s the carb intervention threshold for adults with T1D, at low risk of hypoglycemia, exercising intensively. The recommended target goes up to 145 mg/dL for moderate hypo-risk folks, or older people with diabetes (PWDs) with co-existing chronic illnesses, even with moderate exercise. And it jumps again — to 161 mg/dL — for high hypo-risk, even with minimal exercise.
The fact that targets differ under different circumstances is not surprising; For years, patient advocates have been saying “Your Diabetes May Vary.” But it does make for a set of recommendations that’s difficult to make sense of.
The team that assembled these recommendations duly note that they recognize the
The guidance urges PWDs to consider a few things before starting exercise. Nothing revolutionary here: Know the type, intensity, and duration of exercise. Consider timing after eating, know your insulin on board (IOB) level, and check your current sensor glucose reading and trend arrow before starting.
Peppered throughout the guidance, there’s also mention of how best to use the alert settings on CGM devices around exercise:
- Rate-of-glucose-change alerts should be activated on CGM systems that offer them so that PWDs get an audible warning when glucose begins to dramatically drop or rise.
- Hypo alerts “might be set at the highest possible alarm lower threshold at the onset of exercise, which is currently 5.6 mmol/l (100 mg/dL)” in order to help overcome the delay of interstitial glucose readings when levels are dropping during prolonged exercise.
- For children and adolescents in particular, “hypo- and hyperglycaemic alerts should be set at 5.6 mmol/l (100 mg/dL) and 10.0 mmol/l (180 mg/dL) or individualized if required” and remote monitoring via smartphone should be used if possible to alleviate the worries of parents and caregivers.
The document also flags the risk of “nocturnal post-exercise hypoglycemia,” which is common especially among children and adolescents with T1D who exercise intensely during the day.
The authors recommend that overnight, youths “may set the hypo alert threshold at 4.4 mmol/l (80 mg/dL), or even higher in those with a higher risk… to be able to prospectively counteract impending hypoglycemia.”
So what do the top T1D athletes and diabetes exercise experts in America think about this new guidance?
We reached out to competitive cyclist Phil Southerland, CEO and co-founder of Team Novo Nordisk (formerly Team Type 1). He tells DiabetesMine, “I feel they got a lot of the areas right, and having the paper puts us all in a more educated position than ‘before the paper.’ But as you know, diabetes does not play by any set of rules. I think it would have been helpful to have a baseline of non-T1D glucose readings, to see what ‘normal’ really is.”
He says that while he thinks this paper will be very helpful to clinicians and diabetes educators, it would need to be simplified quite a bit to be user-friendly for PWDs. Of course, in fairness, the organizations that produced the guidance are physicians writing for other healthcare professionals.
Sheri R. Colberg-Ochs, professor emerita of Exercise Science at Old Dominion University and author of several books on T1D and exercise, agrees about the guidance’s lack of usability for PWDs.
“The info and tables are a little dense and may be hard for many PWD to interpret that easily since so many scenarios were given,” she tells DiabetesMine. And although the authors of the guidance stated, “this writing group produced modified and novel recommendations,” Colberg-Ochs didn’t think there was much new to see here beyond fine-tuning recommendations for different age groups and health conditions.
“I didn’t find the info to be novel at all,” she says, stating that she felt the authors “just took previous recommendations and added some considerations specific to CGM.” The previous guidance she’s talking about is the groundbreaking international consensus statement issued in 2017, that gave us the first-ever guidelines on safe exercise with T1D (not focused on CGM).
One other thing she objected to was the carb-centric focus. “In surveying over 300 active people with T1D in past few years,” she tells us, “I noticed that many of them actually eat low-carb and may only supplement with protein and fat-based foods, not just carbs, during exercise of varying durations and intensities and afterward. These recs would not be as relevant to their dietary regimens.”
All that said, she still feels the new guidance was “relevant to both clinicians and PWDs.”
In an ideal world, experts would convert this guidance into some sort of web-based “calculator” where PWDs could simply enter their personal parameters, and the program would auto-generate relevant personalized, user-friendly recommendations. But that’s probably a pipe dream.
In the meantime, the recommendations are out there, even though it takes some digging to discover where you fit in. But as Southerland says, “You have to be diligent if you want to succeed in sport, and even more diligent if you want to succeed in both diabetes and sport.”
What if you’re inspired to use a CGM for exercise but don’t have access to one yet? Talk to your diabetes doctor, because insurance coverage for these devices for people of all ages with T1D is (finally) widely available.
Not all that into exercise? CGM can still help you control your diabetes more easily, and keep you safe from all-cause hypos. Southerland, for one, urges PWDs to “embrace the technology. Use it, use it often, and be detailed on your planning and preparation.”