In the past, I´ve often been told that as a type 1, I need to eat before training sessions and races. However, on some occasions I´ve actually found that training on empty can produce more stable blood sugar levels than eating prior to training.
It is not something I do all the time and whilst I am on a relatively low carbohydrate (COH) diet (ca. 80-100gr/day) I fully believe that my body needs COH considering my training volume and mix of intensities. Sometimes I find it easier to manage sugar levels and more practical to train when I haven't eaten beforehand and don't need to take on (many) COH during training: The last thing I feel when getting up at 5:15am for a 6am swim is hunger so that's one reason why I sometimes train on empty. Another example is that I don't want to inject bolus for any food taken on 1-2 hours prior to training as I then have to work out what impact the "insulin on board" will have during training.
The aim is obviously not to drop in a hypo and the success of this depends on a number of factors:
- Time of day and therefore insulin demand
- Intensity and duration of the session
- The body's ability to use fat as fuel rather than COH
Basal rate set up and time of day
An example: 90min swim at 6am
My sugar levels
With my sugar levels at 103mg/dl (5.7mmol) after waking up at 5:15 I didn't eat or drink anything but reduced my basal rate by 30% from 5:30 for two hours. Just before getting in the water I checked again: 153mg/dl (8.5mmol). I ate one piece of Liquorice Allsorts (ca 3gr COH) nothing else. The first 45 mins of the session were at aerobic, low intensity so levels were expected to drop. The second part of the session was mostly high-intensity with a cool down at the end. The high-intensity exercise is reflected in levels no longer dropping but slightly increasing. I finished the set with a level of 99mg/dl (5.5mmol).
Whilst this strategy has proven to work for training and racing in the morning, it doesn't work for me at any other time of the day. With varying insulin sensitivity during the day, training on empty is much more difficult to achieve later in the afternoon or evenings. This is probably also partly because of "insulin on board" from my lunch as my body is not in a fastened state.