Not For Everyone, Apparently
As gift-giving season reached its peak, personal fitness devices such as the Fitbit, the Nike+ FuelBand and the Aduro U-band were especially popular gifts. The ability to track one’s physical activity is an appealing option to many who want and/or need to be in better shape — especially those with, or at risk of developing, type 2 diabetes.
…many diabetes patients do not respond to exercise as a form of management — a condition termed “exercise resistance.”
Exercise has been a well-known method of preventing and managing diabetes (2, 3). Nevertheless, a recent review study showed that many diabetes patients do not respond to exercise as a form of management — a condition termed “exercise resistance.” This study overturns the widespread belief that physical activity can always be used in diabetes management.
Diabetes in the US
To provide some context, diabetes represents a group of metabolic diseases in which individuals have increased levels of glucose in the blood. Within the US population, diabetes affects almost ten percent, and nearly a third are at risk (4). The high blood glucose level in type 2 diabetes occurs because of resistance to insulin, a hormone that signals the presence of glucose in the blood to cells. Thus, type 2 diabetes prevents glucose from entering the cells and being used as an energy source. The accumulation of glucose in the blood then leads to harm of essential organs such as the kidney and the heart (5). The prevalence and severity of the disease and its burden on patients and the healthcare system add to the importance of studying the disease and its management.
According to authors of the review, Dr. Natalie Stephens and Dr. Lauren Sparks, nearly one in five type 2 diabetes patients do not show metabolic changes in response to serious exercise programs, which suggests exercise is not always effective in limiting diabetes complications. With this finding, the authors then sought to understand the molecular mechanisms behind resistance of these individuals to exercise, specifically in skeletal muscle.
Previous research has shown that exercise can modify the promoters, or the regions that control expression, of specific genes — PCG1-α, PPARβ/δ and PDK4 — known to participate in metabolism. Response to exercise is associated with greater expression of these genes, which enables individuals to improve their metabolism. Stephens and Sparks propose that exercise resistance, on the other hand, occurs when the promoters of these genes cannot be modified in a way that leads to greater expression of the PCG1-α, PPARβ/δ and PDK4 genes, preventing the metabolic changes normally caused by exercise.
Their proposed model is represented in a figure they included in their paper, shown below:
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Image taken from paper by Stephens and Sparks
Although this term accurately describes the molecular model they propose, it implies that certain people are at an inherent disadvantage.
According to the authors, those with exercise resistance are “programmed to fail.”
This research may impact how diabetes is viewed in society. The lack of control over management or prevention of diabetes may reduce the stigmatization and the attribution of characteristics like laziness and poor eating habits to diabetics. On the other hand, exercise resistance may reduce incentives to live an active lifestyle, even though this has many beneficial effects beyond metabolic response. Although this paper merely represents a model, it presents a plausible argument and gives us the opportunity to more closely analyze diabetes management and to question the notion of exercise as a panacea.
Sources
Stephens, N. A., & Sparks, L. M. (2014). Resistance to the Beneficial Effects of Exercise in Type 2 Diabetes: Are Some Individuals Programmed to Fail? The Journal of Clinical Endocrinology & Metabolism, jc.2014–2545. doi:10.1210/jc.2014-2545
http://press.endocrine.org/doi/pdf/10.1210/jc.2014-2545
http://www.nejm.org/doi/full/10.1056/NEJMzoa012512
http://www.diabetes.org/diabetes-basics/statistics/cdc-infographic.html
http://www.diabetes.org/diabetes-basics/type-2/facts-about-type-2.html?loc=db-slabnav