Current exercise guidelines for type 2 diabetes patients offer no recommendations regarding goals for increasing fitness levels and are identical to recommendations given to all adults. Our current knowledge as to how to optimise the effect of exercise as part of an effective treatment approach for type 2 diabetes patients is sadly lacking. It is becoming increasingly clear that an individualised approach is necessary, but the only way to develop an evidence-based individualised approach is for further large-scale, randomised controlled trials to be conducted.
Type 2 diabetes is a chronic disease that doubles the risk of dying from a cardiovascular-related event. It affects over 3 million people in the UK and its treatment and its complications costs the NHS around 10% of its annual budget. The disease is characterised by persistently high blood sugar levels caused by poor tissue responsiveness to the insulin our pancreas secretes, along with inadequate amounts of insulin being secreted.
The onset of type 2 diabetes is influenced by who we are (genetics) and what we do or what we are exposed to (the environment), and as such it can be a difficult disease to manage. It is, however, suggested to be a lifestyle-related disease, because convincing evidence indicates that the risk of type 2 diabetes is hugely increased in individuals with a physically inactive lifestyle. The natural antidote to physical inactivity, physical activity, has become a central part of clinical treatment recommendations for patients with type 2 diabetes.
Clear evidence shows that increasing our physical activity level (e.g. walking, manual work), as well as reducing our physically inactive habits (e.g. sitting, taking lifts/escalators, driving), reduces the risk of developing type 2 diabetes. Furthermore, implementing regular structured exercise in patients with type 2 diabetes can improve control of their blood sugar levels. For these reasons, type 2 diabetes is considered to be a preventable, lifestyle-related disease.
Current clinical treatment recommendations suggest that patients should perform >150 minutes/week of moderate aerobic exercise spread over >3 days/week, resistance exercise >twice/week, and reduce sedentary time (prolonged sitting). Such approaches have proved to be generally effective but there is enormous variability in the beneficial response to such recommendations between patients; some patients respond very well while others do not at all.
The variability in response to a clinical recommendation is rather alarming but is perhaps driven by an over-simplification of what is otherwise a very complex task. Drug prescription in diabetes treatment does not follow a ‘one size fits all’ approach so why would we assume that exercise should? The evidence clearly illustrates otherwise.
Groups like mine are attempting to unravel the basis for this variability in the response to exercise. Poor adherence to exercise is a simple explanation. Exercise dose (e.g. the amount, the intensity, the duration) also influences the outcome. However, when these factors are controlled for, the variability persists. Genetics, i.e. “who we are”, indeed explains some of the variability but only a very small part of it. This leaves the environment, i.e. “what we do” and “what we are exposed to”, as the likely leading cause of the variability. But this is complex and may include several factors, such as the drugs, inflammation, and hormones.
An individualised approach is likely necessary, but the only way to develop such approaches is to create an evidence-base which has been informed by outcomes from large-scale, randomised controlled trials. To facilitate this, funding bodies and politicians have a duty to show a clear interest in financing such work. In the U.S., the National Institute of Health recently launched a new “Common Fund” initiative to comprehensively evaluate and identify the factors influencing adaptation to physical activity in various tissues and organs. This could and should be implemented in Europe.
The notion that “exercise does not work for me” should be an absurdity, because the genetic basis that supports such a statement is only present in a very small number of individuals. All other factors which might contribute to the variability in the adaptation to exercise are controllable.
This means that we, as clinical research scientists, have great potential to drastically minimize the large variability in the beneficial response to exercise in diabetes patients. We just need the right tools and resources for the job.
Our goal is to find a solution and maximise the beneficial effect of exercise for all, to identify the so called “non-responder”, and to apply approaches that will remedy the situation turning the non-responding patient into a responder.
But to do so, we need increased support.
Thomas Solomon, Ph.D.
Senior Lecturer, School of Sport, Exercise, and Rehabilitation Sciences
European Commission Marie Curie Research Fellow, Institute of Metabolism and Systems Research
References:
1. Bouchard et al. Mayo Clin Proc. 2015 Nov; 90(11):1533-40
2. Solomon et al. Diabetes Obes Metab. 2013 Nov; 15(11):987-92
3. Solomon et al. J Clin Endocrinol Metab. 2013 Oct; 98(10):4176-86
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