Studies suggest that up to 20% of people with type 2 diabetes may be exercise resistant—meaning that they do not see any improvement in glucose level when following a supervised exercise regimen, according to a systematic review published in the November 20th issue of the Journal of Clinical Endocrinology & Metabolism.
Dr. Sparks and co-author Natalie A. Stephens, PhD, reviewed the published and unpublished data from animal and human studies on the effects of exercise resistance in response to chronic exercise training in skeletal muscle in people with type 2 diabetes. They found that approximately 15% to 20% of these individuals do not see any improvement in glucose control, insulin sensitivity, or muscle mitochondrial density (a measurement of fat-burning capabilities). Genetic and animal studies suggest that this exercise resistance may be linked to DNA sequence variation and/or epigenetic modifications.
"More research is needed to determine which people with or at risk of developing type 2 diabetes will respond to an exercise program and which will not," Dr. Sparks said. "Genetic and epigenetic patterns could hold the key to differentiating between the two groups. With that information in hand, we can target specific interventions and treatments to the individuals who will benefit most and identify novel treatment approaches to help those who do not respond to exercise," Dr. Sparks said.
Large Individual Differences in Exercise Response
"One major conclusion from the published literature is that there are large individual differences in the response to regular exercise in terms of changes observed in insulin sensitivity," commented Claude Bouchard, PhD, John W. Barton Sr. Chair in Genetics and Nutrition, Human Genomics Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA. "Why do these differences among people exist is not known. We have no idea why some people experience no improvement in insulin sensitivity while others improve dramatically after exposure to the same exercise program in which compliance with the exercise prescription is not an issue," Dr. Bouchard said.
"Thus the authors are addressing an important question," Dr. Bouchard said. "Their suggestion that genetic variants and epigenetic markers are responsible for this degree of heterogeneity in the responsiveness to regular exercise is a sensible one. However, rather than focusing only on known candidates, I believe that an understanding of the drivers of human variation in human responsiveness to regular exercise will require unbiased genome-wide and epigenome-wide screens," Dr. Bouchard added.
"This paper provides additional impetus to the concept that personalized approaches are essential for implementation of successful exercise prevention and treatment programs for type 2 diabetes," Dr. Bouchard said. While this study may uncover the potential that exercise may not have an increased benefit on diabetes, but it still can help reduce the risk of other co-morbidities associated with diabetes.
January 14, 2015
Stephens NA, Sparks LM. Resistance to the beneficial effects of exercise in type 2 diabetes: are some individuals programmed to fail? J Clin Endocrinol Metab. 2014 Nov 20:jc20142545. [Epub ahead of print]