Is the 'Fat & Carbs' datafield supporting to control diabetes during excercises?

End of January 2023, I have been diagnosed with Diabetes and started an Insuline-regime. The usage of insuline complicates endurance sports (>1 hour) both by hypoglycaemia (blood sugar too low) and hyperglycaemia (blood sugar too high). For people who don’t understand the complication, as soon as you start to inject insuline, the oxidation of carbs is not regulated anymore by the body, but is taken over manually: If you eat too much your blood sugars will rise (above 15mmol/l it is not responsible to sport anymore), if you eat too less you will meat the ‘guy with the hammer’ (if you are lucky) or worse.

It came to my attention that the Xert-‘Fat & Carbs’ datafield has been very supportive to monitor the blood sugar levels. I even trust this value above the readings of the Flash Glucose Meter (FGM).

It is my intention to share expierences and to find out if my experiences could benefit others. And I would like to learn expierences from other users.

My approach
After receiving the diagnose, I decided to maintain my goals to cycle both events. I got some advise that I should change my insuline-regine at days of sport activities: Lower the long term insuline (lantis) to 75% and lower the short term insuline (Aspartin) to 50%. Eat carbs (30-60 grams) just before the sport-activity, do not consume carbs in the first hour and the last hour of the activity, and consume 30 grams of carbs + drink bottle of isotonic sportdrink every hour in between. The advise was also to have a bottle with grenadine present in case of a hypo.

I decided to change the approach regarding the middle of the activity, and to test the ‘Fat & Carbs’-field by measuring the blood level (flash glucose meter and blood tests every hour). It brought me to the following conclusions.


  • The Fat & Carbs-field supports me in my food strategy, even better than the usual advises. As soon as the carbs value is 80grams, I start eating every ‘40 grams of Carbs value in the datafield’, supported by a bottle of isotonic sportdrinks every hour (except the first hour and the last hour).

  • The oxidation of carbs (blood sugar level) strongly depends on the intensity during activity. I conducted a testride. The carbs consumption in the first hour on the flat was similar (65grams) to the next 30 minutes on hilly, punchy terrain. The mathematical model is decribed at ‘Fat & Carbs oxidation rates’. Of course the fitness signature should be accurate.

  • The Flash Glucose Meter (FGM) or a Continuous Glucose Meter (CGM) cannot be trusted because of latency. Latency is present (I think 15 minutes?) because the value is measured in skin-tissue. In rest this is not a problem, but during activity this is not acceptable. I have been confronted with differences of 8 mmol/l - 15 mmol/l.

If other members of Xert with Diabetes (using insuline) with a FGM or CGM would care to share their expierence, we might be able to support other endurance athletes (cyclists and runners) in the future.

I am a Dutch male of 54 years old and a recreative sporter. I use the Xert-platform for both running and cycling. End of January 2023, I have been diagnosed with Diabetes, after experienced the following symptoms: Extreme loss of weight since October 2022 (12kg, of which 5kg muscles), always thursty, drinking a lot of water, peeing every half an hour, loss of sight, always cold and early to bed. I was in training for Tour of Flanders (april 2023) and Paris-Roubaix Challenge (april 2023) since October and my peak power and threshold power were only going down: My TP dropped from 248 watt to 208 Watt, my PP dropped from 930 Watt to 700 Watt. Just before the diagnose, I was hardly able to reach power above LTP during a long ride, so I was not able to reach faster energy. I also had experienced the smell of ammonia, which indicates that the body is burning muscles.

Well, I think it works for me, but I don’t know how it works for others. I am not medical trained and every diabetes-case might be different. It is not an advice, but if we could find out what does work and what does not, it might be great study material for medical research.