The secret to your next PB? This wearable blood glucose monitor

Whether you’re shooting for Olympic gold or simply trying to get in shape, good nutrition is crucial to your success or failure. But here’s the complication: because we all respond uniquely to different foods, you can’t simply adopt someone else’s successful nutrition plan. And, unless you head into a lab, it’s hard to see what’s really happening to your body when you eat certain foods. At least it was. But that’s about to change.

Skin-worn, Bluetooth and NFC-enabled, continuous blood glucose monitors (CGM) can now provide real-time insights into how our bodies react to different foods when creating the energy we need for everything, from staying alive, to training, performance, recovery – even that important work project you need to ace.

Continuous glucose monitors were originally created to provide a reliable and convenient blood sugar tracking for diabetics in real time. But some pioneering companies are adapting the technology to unlock potential health, fitness and performance benefits for non-diabetics.

Supersapiens is one of them. The Atlanta-based company was founded in 2019, by Phil Southerland, one of the brains behind Team Novo-Nordisk, an all-diabetic team of elite cyclists, triathletes and runners. It also lists former director of Team GB Cycling and king of marginal gains, Sir David Brailsford, as an advisor.

Specifically targeted at athletes, the sensor-and-app pairing is designed to help marginal-gains-chasers – at any level – understand how their food choices impact performance. Brailsford’s current project, seven-time Tour De France winners the INEOS Grenadiers is one of the professional teams using the Supersapiens system.

The sell is that for the first time, we can literally get under the skin of performance nutrition and see the body’s unique response to different foods and lifestyle factors in real time, 24-7. The central aim: to discover the stable and sustainable energy sources that best cater for your body’s unique fuelling needs.

That’s the theory. But can this new technology really tip the scales in our favour? And are there benefits for non-athletes, too? We put Supersapiens to the test to find out.

Who’s it for?

The first CGMs were created for diabetics back in 1999 with Medtronics, Dexcom and Abbott bringing various models to market. It wasn’t until 2016 that Abbott launched the first CGM device – the FreeStyle Libre Pro – that didn’t require a fingerstick test. And it’s only now that we’re seeing CGM technology being applied beyond the diabetic sphere.

Supersapiens is aimed at anyone dedicated to getting to peak physical performance. Elite athletes, competitive age-group Ironman athletes and dedicated amateurs. This isn’t for your average person in the street who works out once or twice a week.

I’d count myself as a prime Supersapiens target. As a 42-time marathoner and regular ultra runner, I’m obsessed with experimenting to find ways to shave seconds off personal bests. In fact, I experimented with Abbott’s diabetic-focused CGM and app to see if it could improve my fuelling while running the Half Marathon des Sables back in 2018. (The app crashed quite a bit leading to gaps in the data).

Beyond serious athletes and curious amateurs like me, if you’re a dedicated health hacker you might find the Supersapiens data useful. Though the app presents it in a sports performance context, so you’d need to extrapolate.

Anyone looking for a general health alternative might be better served by British start-up MyLevels. It uses the same sensor-plus-app technology but is geared towards helping regular people unlock the positive health benefits of stable blood-sugar levels.

Either way you’ll need fairly deep pockets to benefit from the fledgling tech. A monthly Supersapiens subscription with two 14-day sensors covering 28 days’ tracking, costs €130 (around £115). MyLevels starts from £200. That’s a significant investment.

How Supersapiens works

The Supersapiens platform uses Abbott’s Libre Sense Glucose Sport Biosensors – a version of its CGM that’s been tailored specifically for sports use. Each sensor sits on your upper arm and injects an ultra-thin filament under the skin where it uses interstitial fluid from around the cells to measure real-time glucose levels.

Normal levels for non-diabetics largely fall between a 90 and 140 mg/dLn range. A reading in excess of 200mg/dL after two hours of eating indicates diabetes and 140-199mg/dL prediabetes. Drop below 54 mg/dL and you enter dangerous hypoglycemic territory. If your levels stay higher than this for a long period after eating, this can be a sign of diabetes.

Those readings are sent automatically, in real time via Bluetooth, to the Supersapiens app (available on iOS and Android). You can also force a reading via NFC at any point, simply by tapping the sensor with your phone. Connectivity is mainly reliable, though we had some gaps where the sensor stopped working in the cold. It’s lowest operating temperature is 4.5 degrees Celsius.

Applying the sensors is a little daunting. Inserting something under the skin feels like vaguely futuristic biohacking that takes a little getting used to. In fact it’s better if someone else does it for you. You’re given an applicator that looks something like an immigration officer’s passport stamp. This grabs the small sensor and the menacing looking ‘needle’ from its case. You then place the applicator on your upper arm and press down to punch the sensor into place.

Despite initial fears, applying the sensor didn’t hurt. There’s virtually no sensation as it’s applied to the skin. At worst you might feel a slight dull ache. An adhesive sticker keeps it firmly in place and you can wear it in the shower, swimming and exercising and pretty much forget it’s even there.

Set up and pairing with the app was straightforward. After an hour for the sensor to warm-up, your readings start immediately. And the temptation to wolf down Haribo to see the graph spike is real. Each sensor lasts for up to 14 days and you’ll need at least a month to build a useful picture of your glucose patterns.

Why blood glucose levels matter

If you’ve ever suffered a mid-afternoon slump or suddenly felt lethargic during a workout, the chances are your blood glucose balance was responsible.

Glucose is your body’s main source of energy, particularly for high intensity exercise. When you eat carbs, your body converts these into glucose to fulfil your immediate energy needs and stores any spare glucose as glycogen in the muscles and liver – your main storage tanks for accessible energy. Once these tanks are full, any further excess glucose is stored as fat.

Your ability to stay lean, focused, energised and perform at your best – physically and mentally – depends on your ability to maintain stable blood glucose patterns.

“Based on physiology principles we know that between 90 and 140 mg/dL can be considered a good range to stay in overall, including when you eat and overnight,” says Federico Fontana, VP of science at Supersapiens. “If your body stays within that range it means your body is working. Daily fluctuations should move within that range.”

But with more than 40 factors influencing your blood glucose balance, from food and drink, to stress levels and how well you sleep, this isn’t always easy. “You can help your body in maintaining homeostasis with different food choices,” says Fontana. “Or understanding what foods make you spike or induce big drops. Those foods you can reduce in quantity and stay in a narrower range.”

By revealing the real-time impact of your lifestyle choices on your blood glucose patterns, Supersapiens is looking to take some of the guesswork out of this. You can start to weed out the factors that cause unwanted peaks and troughs. And the potential benefits are big, for performance and health. When it comes to performance, Supersapiens claims to help you discover things like which carb-loading foods help you arrive at a marathon start line with your glycogen fuel tank full. Or which sources of mid-run fuel provide even and sustained energy without spikes and crashes. And to help identify which post-workout recovery options replenish those glycogen stores most efficiently.

“When you exercise, you should try to associate your feeling with the average glucose during that exercise window,” says Fontana. “That will give you a better understanding if – and where – there is a potential glucose zone for you. Perhaps you’ll feel great at a certain glucose level but feel bad at another.”

This takes a lot of trial and error and you’re left to decode the data yourself a little more than we’d like. But if you’re OK with that, the insights and practical implications for your performance are potentially powerful.

There’s a lot to gain from a general health perspective, too. “High [glucose] fluctuations will trigger some inflammation response,” explains Fontana. “Being exposed to an overall higher glucose level might be potentially bad for your health. So if you can reduce that, it will probably be beneficial. This is where the idea of glucose exposure was developed.”

Supersapiens’ tool could also be used to avoid the consistent overexposure to glucose that can induce some significant health undesirables, such as weight gain, insulin resistance and the increased risk of prediabetes and Type 2 diabetes, heart disease and chronic inflammation.

The app

The Supersapiens app is a complex beast with a lot of data. In other words, it’s not immediately intelligible to an untrained eye. Even as someone who has a reasonable basic knowledge of this area, it took me a while to understand what I was being shown and how best to apply it in the real world. Even after a month, there are areas of the app that I’m still not clear on.

The presentation is slick and enticingly visual enough but you’re often left to translate your stats. It really lacks actionable insights and I found myself doing a lot of research to get the most out of it.

The home screen serves up a live blood glucose readout, with an arrow to indicate your glucose trajectory (up, down or stable). An additional chart provides a visual representation of your peaks and troughs over time against a target range. This is by far the simplest data to understand, where you can see the impact of that cheeky glass of red.

The target range defaults to a 70-120 mg/dL range. It is customisable, but there’s no guidance on how you should identify your optimum target range. A second insights tab reveals your total glucose exposure for the day. This shows whether you’re above or below target at any given time. You also get:

Glucose variability: an indicator of relative stability of your blood glucose for a 24-hour period with a lower mg/dL indicating better stability.
Average glucose: for the previous 24 hours with filters for 7, 30 and 90 days plus all time. You can also see your performance against your target.
Glucose zones: a breakdown of the percentage time you spent in different zones ranging from <60 mg/dL to > 140mg/dL.

You can also create events – time-based snapshots that help you isolate the effects of food, exercise, fasting, stress and sleep for comparison.

When you capture an exercise event, you’re asked to score your rate of perceived exertion (RPE) and how you felt during the session. This is designed to help you identify if your fuelling strategy up to and during the workout was effective or not. In practice, I found it tricky to grasp some of the deeper concepts like using trailing glucose averages coming into an event to ensure you turn up with optimally fuelled and ready to perform.

These aren’t explained in the app and converting the readings into learnings required a level of expertise I don’t have. In future iterations, this really needs to be better coached by the app itself.

Living with it

I bravely tested Supersapiens for a week over the Christmas period. For the first week I ate what I wanted. Then for the first three weeks of January, I went cold turkey on the Quality Street and craft beer, upped my exercise game and focused entirely on staying within the app’s recommended target blood glucose zones, hitting my daily exposure targets and minimising my glucose variability.

I brought in some other devices to help measure the impact. A Lumen breath analyser to track my metabolic flexibility (the ability to switch between using carbs and fat as a fuel source); Withings Body Cardio smart scales to monitor body composition; some Etekcity macro-tracking scales to track my carb intake. I also used a Withings Sleep Analyser to see how my glucose habits might affect sleep quality and vice-versa.

The proof is in the eating

During the free-for-all Christmas period, though perhaps not surprising, it was quite shocking to see how regularly I bust my glucose exposure target. My glucose variability was high and I spent more time in the upper glucose zones. I found being able to visualise all of this very powerful and somewhat addictive. It was easy to discover which types of food and alcohol spiked my sugars worst – clementines and cider seemed particularly spikey. It also revealed just how much the festive season messed up my glucose levels.

To get a real contrast, for a fortnight from New Year’s Day, I worked hard to get my glucose variability number down, finding foods through trial and error that promoted stable blood sugar throughout the day. Green veg, eggs, salmon and walnuts all worked well for me. I obsessively monitored the real-time charts with brief hourly check-ins, to weed out anything that caused spikes and crashes.

In two weeks, I cut my variability from an average of 16mg/dL to 10mg/dL, managed to meet my daily glucose exposure targets with pleasing regularity and saw my average glucose drop to that Supersapiens’ default target. But it was the knock-on effects of religiously following the numbers that really impressed.

Without increasing my exercise, I lost 2kg in weight – mainly from body fat. According to Lumen, I improved my metabolic flexibility by 2.7 per cent. That meant I woke more often from my usual overnight fast with my body burning fat where previously it had regularly still been burning carbs. When I ate carbs, my body was more able to efficiently switch back.

Sleep

In those two weeks, I also noticeably improved my sleep with faster times to sleep and fewer 3am wake ups. And it’s possible that avoiding late-night snacking on foods that might raise my glucose levels had a part to play.

“Eating is a very physical process that increases our metabolism,” says Guy Meadows, founder of the Sleep School. “When you increase your metabolism, you increase your core body temperature. And one of the things you need in order to fall asleep is a reduction in your core body temperature. So that’s another way it impacts our ability to sleep.”

“But the big spanner in the works is what you’ve eaten before,” he explains. “If you eat a high GI, high sugar content meal, you’re going to cause that roller coaster effect in your blood glucose levels. Your blood glucose levels spike because you’ve eaten that chocolate, the glucose rushes into the bloodstream, your insulin response to it removes it all and causes your blood glucose to plummet.”

Meadows explains that if you fall asleep during that time and you get that low blood glucose, then this will lead to nocturnal awakening: “And we know that low blood sugar will lead to more frequent awakening.”

The boom and bust of blood sugar levels can also cause tiredness and lack of concentration during the day. Anecdotally, I also suffered far fewer slumps and grumps with less fatigue and loss of focus during the day. I generally felt energised.

The Supersapiens team is currently conducting research to better understand the relationship between sleep and glucose levels. “We don’t have enough evidence at the moment to understand sleep,” admits Fontana. “But we are trying to understand whether hypoglycemia – especially during sleep – can be a potential barrier to recovery.”

“If you want to promote glycogen replenishment with the food you intake after exercise, you want to have a constant and stable flux of glucose from the liver to the muscle. So any drops, and hypoglycaemia moment, might impair glycogen replenishment.”

Fuel

It was starting to feel like this technology might have more benefits for the general population than perhaps athletic performance. But when it came to running performance there were some useful revelations, too.

I managed to use Supersapiens to isolate the pre-workout snacks – and time of those snacks – that delivered the most sustained, even energy, or at least avoided the nightmare boom-and-bust glucose fluctuations. For me, pairing dried fruit and nuts, or energy bars that combined fruit and nuts, seemed to work well. I also tested different energy gels to try and find ways to top up my energy mid-run without inducing unwanted crashes.

This ability to create a menu of reliable fuelling options and measures to optimise performance and reduce the risk of gastrointestinal issues is the Holy Grail of performance. The Supersapiens platform at least helps you see when you might be at risk of under-fuelling.

But how reliable is the data from CGM devices, and does it really have practical benefits over following established fuelling guidelines?

Stuart Galloway, Reader and Group Lead for the Physiology, Exercise and Nutrition Research Group at the University of Stirling, has used blood glucose monitors – though not the same sensors Supersapiens uses – to track athletes in his research. His findings raise some interesting questions.

“If you’re thinking of the accuracy of glucose readings during exercise we definitely noticed a deviation away, between blood and interstitial fluid during exercise,” says Galloway. “So the sensors overestimate the glucose concentration in relation to what’s measured in the blood. We’ve seen that quite consistently.”

Galloway explains that because interstitial fluid is what the muscle is using, “some would argue that the interstitial glucose reading was more important than the blood glucose reading”.

As part of his research, he put monitors on athletes during a 24-hour ultra running race and tracked everything they ate and drank. But it wasn’t glucose levels that made the difference in performance. “We found that how much carbohydrate they were ingesting was a better predictor of the distance they ran in 24 hours,” he says, “and not what was happening to blood glucose.”

However, Galloway does suggest that real-time glucose tech might be beneficial for some athletes who are underfuelling. “If you’re in a low- or no-fuelling zone,” he says, “this could help your work towards the guidelines.”

So, should I buy it?

If you’re an elite – or aspiring elite – athlete who loves digging into data in search of a performance edge, and you’ve got money to spare, this is a tool that gets you thinking about how you fuel your body.

If you have a coach who can help you decipher and apply the insights, there is some ground-breaking data here with the potential to improve your race fuelling. Though the real benefits may well lie in helping you make broader lifestyle changes, such as improving your sleep, that could send you into competition in better overall shape.

If you don’t have an expert coach in your locker room, be warned: this isn’t the easiest app to penetrate. You’ll have to be willing to get stuck into some complex nutritional science and embark on serious self-experimentation to unlock its true potential.

Though the technology arguably reveals as much for non-athletes as it does athletes, its sports focus means anyone thinking about health is probably better off waiting until a more general health maintenance glucose monitoring tool comes along. We’re pretty sure that won’t be long.

A Supersapiens subscription is €130 a month, including two 14-day Abbott Libre Sense glucose sport biosensors.

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