Our expert says:
Ideally, you should aim to eat at least 90 minutes to 2 hours before you start exercise. What happens when you eat is that your insulin levels rise. This happens so that your blood glucose can return to normal. When you exercise however, your blood glucose levels are controlled by another process altogether. Therefore, if you exercise and have this sudden increase in insulin (if you eat before exercise for example), you run the risk of becoming hypoglycaemic. Therefore, what you have to do is to eat about 90 minutes before, so that the food is properly absorbed, and the associated insulin increase has passed. I hope that's not too technical to follow. Now, obviously, the time depends on what you eat - if it's a really light meal, you can get away with eating a little later - say, 60 minutes before. So, it's up to you, but I would say that a minimum of 60 minutes will do.
Now, one other thing that may be cause for concern is that very few people feel light headed right away when they get out of bed. One possible alternative to being low on sugar is that you stood up too fast, and this actually affects blood pressure, so I'm not convinced that your problem that morning was caused by not eating. Many people experience this when the exercise without eating, but to wake up and feel this way is very unusual. Therefore, it may be a once off event, and not something to worry about too much. Having said that, I know you have seen a dietician, but even the fact that you are meticulously weighing your food makes me worried that perhaps your diet has become very precise and from experience, when people start weighing their food, it often means they are not eating enough. However, I'm not the person to comment on this.
GOod luck in the race - I hope that it goes well, and keep up the running.
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