Exercise does affect blood sugar, and for that reason it can make your efforts at blood sugar control slightly more difficult if you’re taking insulin or sulfonylurea blood sugar-lowering medications. The benefits, however, are so great that if you’re a type 2 diabetic, you’d be foolish not to get involved in an exercise program.
For years, guidelines for the treatment of diabetes have repeated the half-truth that exercise always lowers blood sugar levels. In reality, physical exertion can indeed lower blood sugar via increased umber and mobilization of glucose transporters in muscle cells. Certain conditions, however, must be present: exertion must be adequately prolonged, serum insulin levels must be adequate, blood sugar must not be too high, and for most of us, exercise should not be performed within 3 hours of arising in the morning (See Here).
Moderate to strenuous exercise, such as swimming, running, weight lifting, or tennis-as opposed to more casual exercise, such as walking-causes a immediate release of “stress,” or counterrevolutionary, hormones (epinephrine, cortisol, et cetera). These signal the liver and muscles to return glucose to the bloodstream by converting stored glycogen into glucose. The non-diabetic response to the additional glucose is to release small amounts of stored insulin to keep blood sugars from rising. Blood sugar therefore will not increase. If a type 2 diabetic without phase I insulin response were to exercise for a few minutes, his blood sugar might increase for a while, but eventually it would return to normal, thanks to phase II insulin response. Thus, brief strenuous exercise can raise blood sugar, while prolonged exercise can lower it.
Based upon the above information, casual exercise such as walking will not raise initial blood sugar and prolonged casual exercise will definitely lower it. I might also add that an exercise with a lowered pulse rate will burn fat rather than glucose. And we know that by reducing fat we make our insulin more effective, lowering our numbers even more. This would apply to both T1 & T2’s. Even the injected insulin a T1 must take would work better in this case. The T2 would need to produce less insulin, thereby reducing blood sugar numbers and the stress placed on the pancreas. Once fat reduction and lowered numbers had been accomplished, a more rigorous exercise routine could be utilized.
Think of the insulin resistance caused by fat like this: You have two cloths; one is thin and loosely woven and the other is thick and tightly woven. When you pour the same amount of water through each the loosely woven one (less fat) will allow the water to go through faster and the thick woven one (more fat) will greatly slow it down. Of course, in this case the water is the insulin. Think of it this way, the more fat you add the thicker the cloth becomes making the water flow (insulin) even less.