It's well known that exercise reduces blood glucose levels in people with type 2 diabetes. And now it looks like it's better to exercise a few hours after your last meal.

Researchers at the Quebec Heart Institute studied the impact of the amount of time that passed since the previous meal on the blood glucose response. They found that the greatest reductions were seen 4 to 5 hours after the last meal. (See table) Blood glucose was not reduced in people who exercised first thing in the morning, after fasting.

Hours After Eating	Reduction In Blood Glucose Levels(mmol/L)
0-1	28
1-2	33
2-3	35
3-4	38
4-5	43
5-8	23
Fasting	0

So - to get the most out of your exercising -- don't exercise before breakfast. The best time to exercise, when you'll get the best glucose control benefits, is after work. For example, if you have lunch at 1 o'clock and then exercise on your way home from work at 5 to 6 p.m.

Source:  Poirier P, Tremblay A, Catellier C, et al. Impact of time interval from the last meal on glucose response to exercise in subjects with type 2 diabetes. J Clin Endocrinol Metal 2000; 85(Aug):2860-4.