Apologies for reviving this topic - I have only just joined the forum. HbA1c is something I’ve been dealing with for the last 18 months.
A quick internet search will reveal HbA1c is discussed regularly on running and cycling forums. The recurring theme is athletes who have high or pre-diabetic long-term blood sugar levels, but ‘normal’ fasting blood sugar. This was my experience too.
My internet searches found there has not been much medical research into athletes’ long-term blood sugar levels. However I discovered a couple of interesting research papers (sorry no references). The upshot: there is some evidence endurance athletes can have higher HbA1c results than non-athletes; and that athletes who incorporate strength training (e.g. interval work which favours carb metabolisation) can have higher HbA1c than endurance athletes.
One simple explanation for this is that energy demands during exercise - particularly intensive exercise - put glycogen into the blood stream which otherwise would not be there.
Pre-diabetes has become an issue because of the increase in cases of type-2 diabetes. As part of my “treatment” I attended a pre-diabetes workshop. I was the only 65kg, vegetarian, life-long cyclist there. I didn’t really fit the demographic for the rest of the group, and on raising this with one of the Doctors present his response was, “Yes, and think how bad your blood sugar would be if you hadn’t looked after your self”!
My observation from this is some doctors do not understand the statistical modelling behind pre-diabetes diagnosis. It’s a model based on an overweight and inactive demographic. If a person fits the demographic and has a high HbA1c then he/she may be at risk of developing type-2 diabetes.
However, the model may not say much about people outside that demographic. In fact what it might indicate (given normal fasting blood sugar levels) is that athletes have a heightened sensitivity to insulin.
Something I learned which I have taken on board is about diet. The last 50 years have seen the demonisation of fats, whereas contemporary thinking is that carbs are the real danger. I have tried to ‘re-wire’ my relationship with dietary fats (not easy after a life-time of fat avoidance). I eat less bread and potatoes now and make up the deficit with more dairy and nuts. But I have to be careful about weight loss now - my body weight is much more sensitive to the exercise/ food balance.
The advice I would have liked 18 months ago following the pre-diabetic HbA1c assessment is: “Ask straight away for a fasting blood sugar test, and if that is okay avoid going back to the Doctor.”
My brother - who is a nurse and a cyclist (with a lower bmi than mine) advised me, if I was really worried, go and see a sports dietician.