Charles Dumke, a UM associate professor of health and human performance, outfits graduate student Nate Keck with equipment necessary for metabolic testing.

Exercise Enigma

Diabetics in study burned fat faster

By Chad Dundas

At the bottom of his faculty biography on UM’s website, Charles Dumke lists one of his extracurricular interests as: “Selling the idea that exercise is medicine.”

As an exercise physiologist and professor in health and human performance at UM, that mission statement has defined much of Dumke’s research into exercise nutrition, fuel utilization and energy expenditure for the past 17 years. Nowhere is it perhaps more applicable than in his ongoing research into Type 1 diabetes.

Dumke came to Montana three years ago from Appalachian State University in North Carolina. He has worked with diabetics for some time now, both consulting with diabetic athletes training for Ironman triathlons and attending exercise camps for Type 1 diabetics all over the country. One such trip to a Chicago camp back in 2008 belatedly earned Dumke some unexpected media attention recently, after the surprising results of a test he conducted netted him the opportunity to present his findings at the annual conference of the American College of Sports Medicine in Denver in June.

Given what he describes as “an unbelievable paucity of research out there on Type 1 diabetes and exercise,” Dumke set out to compare fuel utilization in “Type 1s” (as they’re sometimes called) to healthy adults by conducting incremental exercise tests to exhaustion on 29 attendees at the camp. Those results were then cross-referenced against a control group of people who don’t have diabetes.

Individuals with Type 1 diabetes suffer from a disease that differs from the more talked-about Type 2 diabetes — which is brought on by lifestyle choices — in that it may be genetic, is autoimmune in nature and is caused by the body’s destruction of insulin-producing cells in the pancreas. The lack of insulin leads to an increase of blood glucose and results in Type 1s facing a lifelong regimen of managing their levels through injections and the use of insulin pumps. Maintaining the delicate balance between insulin and glucose can make exercise risky and difficult for Type 1s, so the more we understand about how their bodies react during the physical stress of a daily workout, the better.

“It’s a complicated interaction, which is what makes it such an interesting scientific investigation,” Dumke says. “Ours was kind of a relatively simple study, but it was a rare opportunity because when do you get 30 Type 1 diabetics of similar age range and fitness all together at once, with the capability to do these measurements?”

Simple study maybe, but when he got around to analyzing the results of the three-year-old study in preparation for last summer’s ACSM conference, what he found was a bit unexpected.

Dumke expected to see no difference in the fat and carbohydrate oxidation rates of the Type 1s and the control group, but it turned out that, at least under the specific circumstances of this test, the diabetic group was burning more fat and fewer carbs. Dumke says this likely occurred because participants were asked to fast for two hours before climbing on a stationary bike or treadmill to take the tests. That fast no doubt resulted in lower insulin levels in the Type 1 diabetics, despite their higher blood glucose levels, and, as a result, more fat expenditure.

“Insulin is a very powerful inhibitor of fat use, so when they have less insulin and they have high blood glucose, what’s the fuel left to use? It’s fat,” Dumke says. “So the practical application of that is that insulin not only controls how much glucose is taken up into tissues, it’s also regulating the type of fuel you are using.”

In certain ways, these findings present Dumke with the age-old dilemma of the research scientist. To the layperson, the average newspaper reader or the reporters who knocks on his office door, the eternal questions are: What does it all mean? How will it affect us? How can we use it? While Dumke certainly understands that impulse, he’s somewhat loathe to talk about the possible real-world implications of this research. The last thing he wants is for a bunch of people to start trumpeting from the rooftops that diabetics might gain an exercise advantage if they start reducing their insulin levels.

“I don’t want that to happen,” Dumke says. “I have to be very cautious because there’s a huge individual variability between Type 1 diabetics, and I don’t want generalized statements from a research study to become individual consulting. That’s a danger, and I don’t want that message to go out there.”

What’s important, Dumke says, is to make sure that Type 1 diabetics and their health care providers — whether it be nutritionists or endocrinologists — use the information to increase their overall understanding of how diabetics can and should safely exercise. Many Type 1s who exercise regularly are probably already lowering their insulin intake beforehand, and Dumke’s study just provides them with a more complete picture of what’s happening inside their bodies when that happens.

“That is a very common thing,” he says. “A lot of Type 1 people, when they exercise, typically have instructions from their endocrinologist to lower their insulin administration because insulin and exercise can be similar in their ability to take up glucose into tissue. So when they exercise with insulin, a Type 1 diabetic is already in jeopardy of causing a hypoglycemic low. Their instructions then are to lower insulin when they exercise in order to lower that risk. That then, we found, predisposes them to using more fat.”

Some Type 1 diabetics have come to terms with how to properly exercise, but others are still struggling with it, some too fearful to even try. Very real concerns about hypoglycemic lows and diabetic comas make it even more important that Type 1s get the proper education and instruction on how to exercise the right way, Dumke says.

“When I showed up at these camps, I was all excited about getting them (Type 1 diabetics) some exercise, and here they are, afraid to do any exercise,” he says. “By giving them more of a well-rounded background in exercise physiology, they felt much more comfortable in being able to understand this [insulin-glucose] interaction. That was a really profound realization for me because I’m usually in the lab doing research and don’t always have that one-on-one consulting experience.”

In other words, it was a matter of selling the diabetics on the idea that exercise is medicine. No worries for Dumke though, who at 45 years old himself looks fit as a fiddle from a regular regimen of biking, running, swimming and triathlons. That, coupled with his knowledge, makes him a pretty good salesman.

For more information email charles.dumke@mso.umt.edu.

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