Secret #28 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 (www.shericolberg.com) for more details or to order this book online.
Although your muscles account for only about 40 percent of your body weight, they can take up 80 percent of any glucose load that you get through your carb intake. Thus, by enhancing the muscles’ capacity to take up glucose with or without insulin, exercise comes closer than anything else to “erasing” your mistakes with your food, insulin, or other medications that lead to hyperglycemia. For example, people can eat more carbohydrate and process it more effectively following hard or prolonged workouts, but usually not at other times.
Much of this effect has to do with improvements in the action of insulin (naturally produced or injected) in your body following physical activity. When your insulin works better, you need less of it to have the same or even a greater glucose-lowering effect. As mentioned, the greatest enhancement in insulin action occurs in the few hours following exercise when your muscle glycogen is most depleted and requires replenishment. During this time, you will likely need considerably less insulin to process any carbohydrates that you eat, and you can get away with eating more carbs after exercise, particularly if it was strenuous and prolonged. In addition, athletic muscles store less excess fat in them, which increases their responsiveness to insulin.
Dr. Sheri finds that her blood sugars react less to her carb intake for several hours or days after physical activity, which is what she would expect. Insulin action actually stays enhanced during most of the time that muscle glycogen is being replaced, which can take as short a time as several hours to replace or as long as two days or more, depending on how much you used. Following long-distance exercise, many people experience greatly enhanced insulin action for at least a day or two, although the effect diminishes over time. Eating carbs during this period of time is likely to have less than the usual impact on your blood sugars.
As discussed earlier in this book, Bob Cleveland finds he can go all day on his long-acting Lantus insulin only when he’s cycling. Many other diabetic athletes over the years have told Dr. Sheri similar things. Very few of them use much short- or rapid-acting insulin when they’re physically active over an extended period of time because of the muscles’ ability to take up glucose without insulin during exercise. Then they have to watch out for lows that hit them after the exercise is over, during the time when their bodies are replacing muscle glycogen.
“Exercise is the biggest thing to do,” says Jim Turner. “It will erase so many mistakes.” His insulin requirements are much lower during and for at least a day after a good workout. “And I eat more carbs, too,” he says. Similarly, Bill King’s strategy is to start with good blood sugar control and earn the right to eat something like a dessert—by working out first. “I still limit the quantity I eat, though,” he says.
Many others, both type 1s and type 2s, who use insulin are able to cut back on their doses depending on their amount of activity. As Chuck Eichten has found, exercise can often substitute for another insulin dose, and for anyone who doesn’t have to take insulin, it can make naturally produced insulin work so much better that the effect is similarly positive for type 2s. Robert Mandell, who has only been using insulin to control his type 2 diabetes for the past six or seven years, says, “If I can get in a week of regular exercise, at night I don’t need any insulin even though I normally take ten units of NPH then.”
If your blood sugars are running consistently above normal any given day, you can often get them back into a more normal range with some exercise. Many regular exercisers with diabetes (and who take insulin) know that if their blood sugars are over 300 mg/dl, they can give a unit or two of rapid-acting insulin and exercise, and the glucose-lowering effect of exercise will be all the more enhanced. “In the past, I have been near 400, taken half the rapid-acting insulin I normally would, gone out to exercise for forty-five minutes, and been near 100 when I was done,” says Dr. Sheri. You have to be careful, though; always take much less insulin than you’d normally need to bring you back down to normal. These days, her blood sugars seldom exceed 250 mg/dl, but she keeps the practice in mind. “Oftentimes if I’m around 150 at bedtime and want to be closer to 100, I can choose to either take a unit of Humalog or ride my stationary cycle at an easy pace for twenty to thirty minutes. I usually choose the latter, and it works really well—usually twice as fast as the insulin ever does.” If you do a moderately paced exercise, even ten minutes may be enough to lower glucose levels, but avoid really intense workouts that may temporarily raise glucose levels when you’re trying to lower them instead.
Endorphins, another natural “eraser” of glycemic mistakes, are mood-enhancing hormones that bind to your brain’s natural receptors and cause feelings of euphoria or a “second wind” after you have been exercising for a while. There is evidence that endorphins may actually improve your body’s insulin action, thereby reversing or decreasing insulin resistance as well. In fact, endorphin release may be a major mechanism in the enhanced insulin sensitivity attributable to moderate exercise training. If that’s the case, go for maximal endorphins on a daily basis to control your blood sugars, and as a side benefit, you will be less depressed and anxious and enjoy a greatly improved mood.
Finally, even though physical activity will allow you to be a little more slack in your diet and still control your blood sugars, this effect works only up to a point. Diabetes is not just a carbohydrate-processing disorder; it is also a disorder of blood fats, which when elevated can contribute to the development of plaque formation in arteries and circulatory problems throughout your body. Your food intake can affect your glucose levels and your blood fats, as can your exercise habits, so optimize them by balancing your exercise and your diet for the greatest longevity.