An important part of getting fitter, and improving both speed and endurance is training the body to burn fat at higher levels of intensity. This is really important for athletes who do the things I like doing – running (because they can go faster and further) and mountaineering (because mountaineers don’t have very good access to food to top up their limited carbohydrate stores).
One of the advantages of having diabetes is that I can observe how much carbohydrate I need to eat to keep my blood sugar stable. Does this mean that I have an insight into how well my body is adapting to burning fat? Can this help anyone else?
What does my data say about “fat adaption”
I’m currently training for an ultra-marathon in the Brecon Beacons in two weeks time. (Finishing it in fourth place last year was probably the proudest moment of my life, and one which will be very hard to emulate – I now know that I can run ultras with diabetes and run them fast – so what magnitude of challenge do I need to take on to face that level of “unknown” again?) When running with diabetes it is very important to understand how much carbohydrate one must consume to keep blood sugar levels stable. So I keep data on it.
The fact: I need to eat less carbohydrate during long low-intensity exercise than I did a year ago.
Lots of things have changed over the past year. My requirement for long acting insulin has increased. I take twice as much long-acting insulin now than I did last year. The more insulin I take, the more carbs I need to eat during exercise. So it could just be that I don’t take enough long-acting insulin now – even though I take more than I used to. But it seems to be appropriate for my blood sugar generally so I’m not sure if insulin dosage is the culprit.
I was always fit, but compared to last year I have built a huge endurance base: in theory, my body has adapted to burn more fat at higher exercise intensities. This is important for endurance because the body stores a lot more fat than carbohydrate so it prolongs the moment when the carbohydrate stores are fully depleted and the athlete “bonks”.
So does the fact that to maintain stable blood sugar, I need to eat less carbs whilst exercising than I used to mean that I burn more fat and less carbs for energy? (Or does it mean that I will bonk sooner because I’m not replacing carbs at such a high rate?) I think it probably means the former.
Finally, traditional exercise nutrition recommends that an athlete consumes 60-70g of carbs an hour (for my weight). I’m not sure many ultra athletes eat that much, but should I be aiming to eat as much as possible or is it just not necessary? I would love any sports nutritionists who are reading this to give me their opinion.
Before the CCC, I took a bit less long-acting insulin than usual because I was again stepping into the unknown and was afraid of getting a hypo. It turned out that it wasn’t enough and my blood sugar stayed at the top of its safe range for the first seven hours of the race despite me eating less than 5g an hour of carbs on average. I was struggling by half-way (where I took some more insulin and ran the second half eating about 40g an hour) but it was a lesson in how amazing the body is at functioning with almost no additional fuel!
Intense exercise burns more carbs but can also delay the need to eat any
When exercising at high intensity, the body has to rely on the carbohydrate metabolism more. But because of this, the liver dumps some stored carbs into the blood in anticipation. This means that for me, if I sprint, my blood sugar will initially go up. I also find that doing interval training raises my blood sugar – and delays the need to eat – more than doing the same distance and time at a steady pace.
I love burning carbs!!
Since learning about building an aerobic base, I do most of my exercise at a relatively low intensity to optimise that fat burning process. And I’ve seen amazing results at both endurance and speed. But interval and speed training is important too. I love the feeling of having exercised hard – it can come from doing a really intense training session or from running a really long way. I love that tired feeling in my legs. I have no idea about the science, but I can almost feel my body’s craving carbs to replace its depleted glucose stores. When I feel like that, I know that I need to eat a lot of pasta and that I will hardly need any insulin to manage my blood sugar. This heightened sensitivity to insulin following exercise is why exercise is so important for people with type 2 diabetes or insulin insensitivity.
Exercise is surely good for everyone’s blood sugar control
Since getting back into training properly about three weeks ago, my blood sugar upon waking has been between 5 and 6 mmol/litre almost every morning (despite it sometimes being bit haywire at times when going to bed), a level which is basically perfect – well done me! It’s definitely good for my peace of mind to know that I am minimising long term damage to my body by running a lot.
That is why exercise is so important for people with type 2 diabetes or insulin insensitivity.
And apart from all this complicated stuff about blood sugar control, exercise and adventure are just good for the soul. Going back up into the mountains over the past few weeks and running for hours at a time is wonderful. Surrounded by walls of rock, snow, and wild animals, breathing cold air and putting one foot in front of the other, I feel strong (if only fleetingly!) and alive.