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Q&A with Dr. Sheri Colberg, Ph.D., FACSM

Feb 13, 2016

 invited reader questions on her article, Just Exercise Harder for Less Time, or Not?. Here are her responses to your questions about HIIT for diabetics and related weight and exercise issues.

Question:  Hello Sheri, While I liked your article overall, I take issue with your description: “The majority of people with diabetes who are older and likely overweight.” I’m a 59 year old male, 6’3″ with a BMI IF 22.5. Oh yes, and an insulin deficient type 2 diabetic.  When you make generalizations, you perpetuate this myth the public at large holds that diabetics are just fat and if they’d only take better care of themselves they wouldn’t have diabetes.  I can’t tell you the number of times people are amazed when they find out I’m diabetic.  While it may be true that there is a large population of overweight diabetics with metabolic issues, there is also a large population of normal weight individuals that are tired of being lumped into these easily thrown out generalizations.  Otherwise   a great write up on the benefits and limitations of HIIT.  –Bill G., 6’3″ with a BMI of 22.5. 


sheri_colberg2Answer:  Bill, thanks for the feedback. Unfortunately, the majority of people with diabetes are older and overweight or obese, including many people with type 1 diabetes, not just type 2. Most of my research has been focused on older people with type 2 diabetes, and in all the years I’ve been doing research (over two decades), I have only had one type 2 who was not overweight or obese participate. My article was mainly addressing what I know about how research studies go. In order to recruit subjects into exercise training studies, most of the time the IRB (Institutional Review Board, which exists to protect subjects) at my university will not allow me to include people with other health problems besides diabetes, which means that I am only testing the healthiest people who are not the norm with diabetes. These are the ones that others have also recruited to participate in high-intensity interval training, which is exactly why I use “the grandmother test” that I mentioned in my article to gauge whether those published results are likely applicable to the population with diabetes as a whole. My grandmother was obese, had “borderline diabetes” as they called it back then, and suffered through every possible cardiovascular complication related to diabetes that you can possibly have during her final 8 years of life. Even when she was younger and healthier, though, there’s no way she would ever have been able to participate in HIIT since she was sedentary, and she wouldn’t have wanted to do it.  The people who do HIIT over the long term are the exception, not the rule, and likely the ones that research is actually testing that protocol out on. That was my point.

Question:  I’ve been T1 for 48 years & been doing HIIT for 20 minutes 5 days a week for 10 years. I consistently have A1c btwn 5.5 & 6.0 & don’t have major complications. Why are doctors so confused about benefits of HIIT for diabetics whether T1 or T2?  It’s been studied extensively at MacMaster & McGill universities & shown to be very effective.  — Walter W.

sheri_colberg2Answer: I agree that doing faster intervals interspersed throughout any workout may have benefits like increased fitness and more stable blood glucose levels during the activity. However, many people with diabetes are not as healthy as you are since most Americans are sedentary and even more with diabetes are less active than normal for multiple reasons (such as fear of hypoglycemia with exercise).  I think that more studies are needed before we can make sweeping statements about the benefits of HIIT for all individuals with diabetes, particularly since so many of them have comorbid health issues, complications, joint issues, and more. It’s great that you’re benefiting from doing it, though.  Keep  it up!

Question:  I go to the gym every other day for about 50 minutes immediately after finishing breakfast.  Will my blood sugar after exercising be lower if:  1. I continue as indicated above or 2.  I wait approximately an hour after beginning breakfast before starting at the gym? — Gordon G.

sheri_colberg2Answer:  I think you should try both out and see what your individual response to each time is. In general, blood glucose levels peak about an hour after eating, but it really depends a lot on what you eat (carbs, protein, fat), whether you give insulin or release your own, and what type and intensity of training that you’re doing at the gym. Exercise generally slows down digestion by pulling blood away from the digestive tract and diverting it to active muscles instead, so being active after eating usually blunts the post-meal rise in blood glucose, but as noted, how much and for how long depend on a lot of other factors.


As a leading expert on diabetes and exercise, I recently put my extensive knowledge to use in founding a new information web site called Diabetes Motion (www.diabetesmotion.com), the mission of which is to provide practical guidance about blood glucose management to anyone who wants or needs to be active with diabetes as an added variable. Please visit that site and my own (www.shericolberg.com) for more useful information about being active with diabetes.