Secret # 25: Exercise Daily (or Close to It)

Secret #25 is excerpted from Part Five: Exercise Secrets found in my new book about what has worked well for long-time diabetes survivors: 50 Secrets of the Longest Living People with Diabetes by Sheri Colberg, PhD, and Steven V. Edelman, MD (November 2007). Check my Web site ( for more details or to order this book online.

Of all the secrets to being successful at living long and well with diabetes, exercise is the one that came up the most consistently as one of the top ones, regardless of how long people had been living with the disease. Given that physical activity can cause low blood sugars —both during and afterward, with a delayed effect— you would think that fewer people would find it important for glycemic control, especially insulin users and people taking certain oral diabetic medications that increase the risk of exercise-related hypoglycemia. However, the majority said that it was one of their primary salvations, particularly before the advent of blood glucose monitors. Dr. Sheri recalls, “I started exercising as a kid way before I ever got a blood glucose meter because it was about the only thing that made me feel better physically. Now, almost forty years later, it still does! I work out doing various activities at least five to six days a week.” Dr. Steve also grew up exercising regularly. He remarks, “Exercise was one of the key things that kept me going.”

Bob Cleveland recalls a summer when he was six or seven years old (over eighty years ago) when his family rented a cabin on a nearby lake. Even then the glucose-lowering effects of exercise were evident to him. “In the two weeks that we were there, I learned how to swim, and I stayed in the water almost all day long. I had been taking lots of insulin, but my mother had to cut back on my doses. She could tell by testing my urine (the only method of monitoring available at the time, albeit an imprecise one). If there was no sugar in it, she cut back on my doses.” At least in modern times, we have blood glucose monitors to check actual levels and to make more scientific, calculated dosage changes to compensate.
Even now Bob still experiences the benefits of exercise on his blood sugars. One of the reasons he goes to Florida in the wintertime is so he can be more active. “If I’m at home in Syracuse and the weather is bad, I’d have to take more insulin during the day and my sugars would still run higher. On most days in Florida, I can ride a bike a long way—yesterday I rode twenty miles—and never have to take any rapid-acting insulin. With all that activity, I only needed my basal dose at bedtime.” While not everyone gets away with cutting out that much insulin, it certainly highlights the fact that exercise allows your body to take glucose out of the bloodstream without much extra insulin.

Why does exercise help your blood sugars so much? It’s because your muscles actually have two separate ways to get glucose into them. When you’re resting, insulin works to do it, but during exercise, muscle contractions themselves cause you to take up glucose without the need for insulin (whether you make it yourself or inject it). Thus, exercise always has the potential to lower your blood sugar levels. The only potential downside is that if your insulin levels are too high when you’re exercising, your sugars can drop rapidly due to the additive effects of insulin and muscle contractions.

“Exercise makes such a big difference,” Rich Humphreys agrees, as does Freddi Fredrickson, who says, “It makes my insulin work much better.” Jim Turner also states, “Exercise is key for blood glucose control.” At a minimum, Jim plays basketball for a couple of hours at least twice a week (“I’m the oldest guy on the court by ten years,” he says), and when he does, he takes much less insulin. The day after, he also eats more carbs for breakfast. Marialice Kern prefers hiking in the California foothills, and she also feels that exercise makes a big difference in her diabetes care. Finally, Gladys Dull says that she knows it makes a difference because before she had a glucose monitor, she only used to get low during her activities—such as cycling, snowmobiling, horseback riding, and more.

Undeniably, engaging in daily (or nearly daily) exercise done consistently makes it easier to manage your blood sugars. Thus, establishing an exercise routine can help you to exercise and balance them more effectively. If you consistently exercise at the same time of day doing a usual activity, by monitoring your sugars before, occasionally during, and afterward, you can establish your glucose response to the activity and determine the best adjustments to make in your food intake and medications. For insulin pump users, disconnecting the pump (or at least lowering basal rates) during activities also helps prevent hypoglycemia because it mimics what a nondiabetic person’s body normally does during exercise—when insulin levels go down. For people with type 2, their bodies will be able to lower insulin levels during exercise naturally.

There is no doubt that exercise can also increase the likelihood of experiencing lows both during and after activities—for as long as twenty-four to forty-eight hours afterward. The immediate effect comes for a greater use of blood glucose during exercise, but delayed-onset hypoglycemia often results from greater insulin action in the hours to days following the activity, which is largely attributable to the replacement of glycogen, your muscles’ storage form of glucose. Your insulin action will be heightened most in the first couple of hours following an activity and diminish over time as your glycogen is replaced. The most effective way to prevent delayed lows is to make sure that you take in some carbohydrate after the activity, since low-carb diets are known to slow the rate of glycogen repletion. Your body may need very little insulin to take up glucose right after exercise, though, so if you take any, cut back on your usual amount of insulin for the number of carbs you’re taking in.


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