Diabetes Type 1 and Exercise

Can we track and manage blood sugar levels in sport? 

Yes; in fact, the way we manage blood glucose levels has improved significantly with the introduction of continuous glucose monitoring (CGM). This has not only been significant in athletes in sport with Type 1 diabetes but it has also started to be accessible to athletes without Diabetes. Perhaps a trend in another way to monitor metrics and data for use of fuel during training sessions and racing. 

Can athletes or people with Type 1 Diabetes exercise and compete in sport?

Yes! People or athletes with Type 1 Diabetes or Type 2 Diabetes are absolutely able to not only exercise but compete in sport. 

With around 40 million people in the world with type 1 diabetes, there are an increasing number taking up sport both amateurly and competitively (1). 

Is it good for people with Type 1 Diabetes to exercise or compete in Sport?

The benefits of exercise are well known and also confer to someone with type 1 diabetes. Exercise is particularly important considering the risk of cardiovascular disease being the leading cause of death in young people with type 1 diabetes (2). 

Are there more benefits to people with Type 1 Diabetes and exercise?

Interestingly the benefits of exercise are extended further in someone with type 1 diabetes including:

1. Blood glucose levels are generally better controlled with fewer spikes
2. Diabetes-related complications including retinopathy, nephropathy and the risk of coma are reduced (2)

Can athletes with Type 1 Diabetes manage blood sugar (glucose) effectively in sport or competition? 

Simply put YES. BUT…..exercise in individuals with type 1 diabetes (or the difficulty of managing blood glucose levels)  can be challenging and increases the risk of hyperglycaemia (high blood glucose) and hypoglycaemia (low blood glucose).

With years of experience in clinical dietetics; with support, education and understanding people with Diabetes (Type 1 and Type 2) can not only interpret but proactively be in control of managing blood glucose and insulin required (if required in Type 2 Diabetes). 

More so, now with the surge in monitoring blood glucose in the athletic population without diabetes; education and the help and support of athletes to interpret the data by a qualified clinical dietitian or professional is the absolute key to interpreting and acting on the data. 

After all, why measure data if you don’t do something with it?!

How does managing blood sugar (glucose) differ in people with Type 1 Diabetes in Sport?

In someone without diabetes, blood glucose levels are kept within a tight range. Our bodies love to be in homeostasis or in a state of balance without too much flux!

Blood glucose is controlled mainly through the hormones insulin and glucagon. During exercise, insulin levels decrease as the muscles start to take up glucose as fuel, and blood glucose levels decrease. Glucagon levels increase and glycogen from the liver is released to match the amount of glucose used by our muscles, keeping our blood glucose levels stable (4).

Do people with Type 1 Diabetes produce insulin? 

An athlete or person with type 1 diabetes does not produce insulin (hormone reducing blood glucose levels) naturally. Therefore the amount of insulin instead, is determined from the dose administered, and so are also unable to decrease the amount of insulin circulating in their system.

The increase in the amount of glucose taken up by the muscles during exercise is not matched by a release of glucose from the liver, therefore decreasing blood glucose levels and increasing the risk of hypoglycaemia (13).

Here is where we realise just how intricate the balancing act is when managing blood glucose for exercise and sport.

Does exercise increase the sensitivity to insulin?

Exercise does increase insulin sensitivity (3,5,6). In an individual with type 1 diabetes, this means you need less insulin for the same amount of carbohydrate further increasing the risk of hypoglycaemia. Not only does it increase risk of low blood glucose during sport but this increased insulin sensitivity can continue for up to 24 hours following exercise. 

People without diabetes also have an increased insulin sensitivity too!

Does sprinting or a TT race cause a spike in blood glucose levels? 

Yes! High-intensity exercise can increase blood glucose levels in people with type 1 diabetes and also athletes that don’t have diabetes!

It’s just not simple …..different types of exercise have a different effect on our blood glucose levels. In general, aerobic exercise (low to moderate intensity) causes a reduction in blood glucose levels.

Anaerobic exercise (high intensity) tends to increase blood glucose with this increase lasting for several hours post-exercise (2). 

If high-intensity exercise is performed in a fasted state this can increase blood glucose levels even further (6). Sports that involve periods of both such as football and rugby tend to have less of an effect as the decrease from aerobic and increase from anaerobic offset each other.

This is where measuring insulin (whether you have type 1 diabetes or not) can be a useful metric to understand how your body reacts to certain training loads.

What about the interaction of other hormones during matches and races? Do hormones affect blood glucose levels in competition for people with Type 1 Diabetes? 

The response to exercise is highly individual plus other factors such as the production of the hormones cortisol and adrenaline, the temperature and humidity can also affect blood sugar levels (3).

So the balancing of insulin dosing and appropriate carbohydrate intake pre, during and post-exercise is essential along with the support of a qualified professional with an understanding of sport. 

There are a variety of methods that can be used to achieve control depending on the on the type and duration of exercise. It also takes a lot of testing, knowledge, data gathering and acting on that data to work out what works best across different exercise scenarios, noticing how the changes in insulin dosing and carbohydrate intake affects blood glucose. 

Do endurance and aerobic exercise cause a reduction in blood glucose levels?

During aerobic exercise; a reduction in blood glucose levels can be balanced through a decrease in the insulin dose of approximately 30-50% before exercise (7) and/or increasing carbohydrate intake before and during exercise for prolonged activity (2,8), preferably low GI prior and high GI during.

So testing and having intricate knowledge of how an athlete’s body reacts individually to different training sessions and competition is vital to helping them manage their dosing of insulin and how much carbohydrate to take on board. 

Is more insulin required during high-intensity exercise in Type 1 Diabetes?

For anaerobic exercise where blood glucose levels tend to rise, a small increase in insulin may be necessary, with a focus on replacing carbohydrates following exercise (2,7). 

Can caffeine decrease the risk of Hypoglycaemia? 

Interestingly, caffeine (200-300mg) may reduce the risk of hypoglycaemia during and after exercise (12)! However, testing is required and this can not be relied on as the only method to prevent hypoglycemia. 

When administering insulin during exercise, care must be taken not to inject into contracting muscles, as the uptake will be increased (13).

All exercise is associated with an increased risk of nocturnal (overnight)  hypoglycaemia, especially aerobic exercise. This increases further if training is undertaken in the latter part of the day (2,11). Think of a track session or late-night swim set!

This is partly because the increased insulin sensitivity seen following exercise can last for up to 24 hours (2). This can be attenuated by a reduction in the insulin dose of between 20-50% at the first meal after exercise and/or increasing the amount of carbohydrate consumed, as well as consuming a low GI snack prior to going to sleep (2,5,10,11).

Educating and testing becomes absolutely essential and key to supporting an athlete with management at night. Seeking advice and support from a sports dietitian who understands diabetes can be particularly useful to support an athlete to understand their data. 

Does sleep affect blood glucose control? 

Yes in both people and athletes with and without Type 1 or Type 2 Diabetes, poor sleep does affect blood glucose control. 

Post-exercise recovery is important and should focus on stabilising blood glucose levels (ideally between 4 and 10mmol/L)11 and preventing hypoglycaemia throughout the rest of the day and night;  replenishing glycogen stores but also maximising training adaptation and recovery prior to the next session.

We know that sleep is an important and overlooked part of recovery. Sleep is vital for performance and optimal adaptation to training. In someone with type 1 diabetes, poor sleep can negatively affect blood glucose control (11).

For all types of exercise, blood glucose levels should be monitored before, during and afterwards. Adjusting insulin doses and carbohydrate intake appropriate to the blood glucose levels measured, the type and duration of exercise and individual requirements.

This sounds easy but for anyone without diabetes and tracking data using CGMs (continuous blood glucose monitors) in sport will know that it takes a lot of testing and understanding of what and how to interpret and act on that data. This is also highly individual. 

Whilst we now have some base guidelines for the management of exercise in individuals with type 1 diabetes the way we respond to exercise is highly individual and any nutritional plans or strategies must be individualised to the athlete.

If you are interested in learning more about managing your blood glucose levels in sport and competition reach out to our team at 4thDiscipline who are qualified high-performance nutritionists but also clinical dietitians with specialist knowledge in diabetes in sport. 

Whether you have type 1, type 2 Diabetes or an athlete who is interested in monitoring blood glucose levels and using CGMs (continuous blood glucose monitors) we are here to help support you on your journey! 

References 

1. IDF Diabetes Atlas 9th Edition. International Diabetes Federation, IDF Diabetes Atlas. Secondary International Diabetes Federation, IDF Diabetes Atlas 2019.
2. Riddell MC, Gallen IW, Smart CE, et al. Exercise management in type 1 diabetes: a consensus statement. The lancet Diabetes & endocrinology 2017;5(5):377-90.
3. O'Reilly M, O'Sullivan EP, Davenport C, et al. "Dead in bed": a tragic complication of type 1 diabetes mellitus. Irish journal of medical science 2010;179(4):585-7.
4. Camacho, R.C., Galassetti, P., Davis, S.N. and Wasserman, D.H., 2005. Glucoregulation during and after exercise in health and insulin-dependent diabetes. Exercise and sport sciences reviews, 33(1), pp.17-23.
5. Keay, N. and Bracken, R.M., 2020. Managing type 1 diabetes in the active population. British journal of sports medicine, 54(13), pp.809-810.
6. Yardley, J.E., 2020. Fasting may alter blood glucose responses to high-intensity interval exercise in adults with type 1 diabetes: a randomized, acute crossover study. Canadian Journal of Diabetes, 44(8), pp.727-733.
7. Franc, S., Daoudi, A., Pochat, A., Petit, M.H., Randazzo, C., Petit, C., Duclos, M., Penfornis, A., Pussard, E., Not, D. and Heyman, E., 2015. Insulin‐based strategies to prevent hypoglycaemia during and after exercise in adult patients with type 1 diabetes on pump therapy: the DIABRASPORT randomized study. Diabetes, Obesity and Metabolism, 17(12), pp.1150-1157.
8. West, D.J., Stephens, J.W., Bain, S.C., Kilduff, L.P., Luzio, S., Still, R. and Bracken, R.M., 2011. A combined insulin reduction and carbohydrate feeding strategy 30 min before running best preserves blood glucose concentration after exercise through improved fuel oxidation in type 1 diabetes mellitus. Journal of sports sciences, 29(3), pp.279-289.
9. Turner, D., Luzio, S., Gray, B.J., Bain, S.C., Hanley, S., Richards, A., Rhydderch, D.C., Martin, R., Campbell, M.D., Kilduff, L.P. and West, D.J., 2016. Algorithm that delivers an individualized rapid‐acting insulin dose after morning resistance exercise counters post‐exercise hyperglycaemia in people with Type 1 diabetes. Diabetic Medicine, 33(4), pp.506-510.
10. Campbell, M.D., Walker, M., Trenell, M.I., Stevenson, E.J., Turner, D., Bracken, R.M., Shaw, J.A. and West, D.J., 2014. A low–glycemic index meal and bedtime snack prevents postprandial hyperglycemia and associated rises in inflammatory markers, providing protection from early but not late nocturnal hypoglycemia following evening exercise in type 1 diabetes. Diabetes care, 37(7), pp.1845-1853.
11. Scott, S.N., Fontana, F.Y., Cocks, M., Morton, J.P., Jeukendrup, A., Dragulin, R., Wojtaszewski, J.F., Jensen, J., Castol, R., Riddell, M.C. and Stettler, C., 2021. Post-exercise recovery for the endurance athlete with type 1 diabetes: a consensus statement. The Lancet Diabetes & Endocrinology, 9(5), pp.304-317.
12. Zaharieva, D.P., Miadovnik, L.A., Rowan, C.P., Gumieniak, R.J., Jamnik, V.K. and Riddell, M.C., 2016. Effects of acute caffeine supplementation on reducing exercise‐associated hypoglycaemia in individuals with Type 1 diabetes mellitus. Diabetic Medicine, 33(4), pp.488-496.
13. Hornsby, W.G. and Chetlin, R.D., 2005. Management of competitive athletes with diabetes. Diabetes Spectrum, 18(2), pp.102-107.