Here are two quick “Did you knows?” concerning fasting, exercise and blood sugar.
Did you know that it takes 30 to 60 minutes of running at 75% of your V02 max (for conditioned runners) to get your blood insulin levels down to the same level found in people who have been fasting for 23 hours? (Dohm LG 1986)
Did you know that when scientists studied people who exercised after fasting for 23 hours, their blood sugar levels were actually found to be slightly higher then when the same people exercised after a small meal? (Coyle EF 1985; Dohm LG 1986)
What this means to you- running at 75% of your VO2 max for as long as 70 minutes in well trained runners who had been fasting for 23 hours did not cause hypolgycemia (low blood sugar) So if you like exercising while you are fasted, this research suggests you don’t have to worry about hypoglycemia (as long as your exercise intensity isn’t way above these levels).
And it takes between 30 and 60 minutes of running at a VO2 of 75% to get the same insulin lowering effect as simply sitting around the house after fasting for 18-24 hours.
Two things to think about the next time you are fasting.