101 Health Series: Type 2 Diabetes Mellitus
Information for Personal Trainers, or those seeking to learn more about Type 2 Diabetes Mellitus
Before we get started, it is important to note the mandatory medical disclaimer so far as to say this article will contain medical information but it is not be misconstrued as medical advice. If you wish to implement any of the information found within this article, it is important to first consult your primary care provider. Now that I’ve covered myself from those feeling a little overly litigious, let’s get started.
Most of us will be aware of diabetes and perhaps have some understanding of it, or even know people afflicted with the condition. The most common forms are Type 1 and Type 2 diabetes mellitus, both of which implicated in improper handling of blood glucose and can cause a vast array of issues. There are a multitude of other forms of diabetes mellitus that can present in a similar fashion with distinct causes. Furthermore, to make it more confusing there is also diabetes insipidus which itself has several distinct forms all of which are involve dysregulation of fluid balance not related to blood glucose.
The focus of this article will be on Type 2 Diabetes Mellitus which I will from here on out refer to as simply T2D. T2D is the most common of all forms of diabetes comprising 90% of all diabetes diagnoses, with 4.7 million people in the UK diagnosed with one form or another (Diabetes UK, 2019). It also is the most responsive to lifestyle modification, there is certainly still a significant genetic component but evidence has shown we have an array of tools to minimise our risk.
Firstly, let’s look in a little more detail at how blood glucose homeostasis is maintained normally in relation to carbohydrate intake. When you consume any meal that contains carbohydrate, it is broken down into its constituent parts. Some require further metabolism beyond the scope of this article e.g. fructose, but the end result by and large is an increase in blood glucose. This elevation is detected by beta-islet cells in the pancreas which release insulin in response, this is followed by the uptake and storage of glucose by insulin-sensitive tissues which include primarily skeletal muscle, adipose tissue and the liver. Now, T2D is the consequence of a state of ‘insulin resistance’, meaning more insulin must be produced to store the same quantity of glucose. Eventually in some cases the beta-cells of the pancreas can no longer produce sufficient insulin to overcome the resistance, thus leading to an increase in blood glucose. The negative effects of persistently elevated blood glucose are numerous, with most of the major long term complications being due to the damage of blood vessels. Damage to larger vessels can lead to conditions such as coronary artery disease, stroke and peripheral artery disease. With damage to smaller vessels leading to conditions such as diabetic retinopathy (damage to eye) and diabetic nephropathy (damage to kidneys). There is also the potential for diabetic neuropathy (damage to nerves) which can lead altered sensation. All in all, it is not the most pleasant of conditions, especially if it is not carefully controlled. Then again there is a wealth of evidence to suggest we can mitigate the risk of acquiring it or managing it effectively if already acquired.
So what does the evidence say can assist in mitigating risk? In its very simplest form; exercise, diet and attaining a healthy weight are the cornerstones. As with anything though, there are additional details that may be able to refine the approach further.
In respect to exercise, current guidelines suggest that 150 minutes per week of moderate intensity aerobic activity and resistance exercise 3 times per week should be performed (Umpierre et al., 2011). Previous meta-analyses have shown that a combination of aerobic and resistance exercise has reliably been able to reduce HbA1C levels; a surrogate marker of blood glucose control (aka glycaemic control) over the past 2-3 months (Boulé et al., 2001). Since then, studies have been performed to test whether there were differential response to either aerobic or resistance exercise alone or in combination. Sigal et al. (2007) found that while both either form alone improved glycaemic control markers, there was a synergistic effect for both combined i.e. greater than the sum of its parts. Church et al. (2010) on the other hand did not find any statistically significant (p <0.05) improvements for either form alone, but did for a combination. Digging a little deeper we can look for trends that may be of value even if they do not quite reach statistical significance which in the traditional format of p < 0.05 has its own limitations (a topic for a particularly dry article). Both Sigal and Church’s results for example show a trend for improved HbA1C with aerobic exercise more so than resistance exercise, suggesting aerobic would be the preferred modality if one had to choose. The mechanisms by which both improve glycaemic control overlap significantly, but there are also differences although it is not fully understood as of yet. Resistance exercise has long been known to generally increase skeletal muscle mass to a greater degree than aerobic exercise. Since muscle is a major site of glycogen storage, it provides a greater buffer to an excessive dietary intake of carbohydrate as well as mitigating the potential insulin resistance that can be induced by high fat diets. Aerobic exercise appears superior in respect to reducing inflammatory markers and beta-adrenergic function which is correlated with an improvement in insulin sensitivity (El-Kader, 2011).
Dietary factors are also a significant component in relation to preventing, delaying or managing T2D. Although it is important to tailor interventions to the individual, some broad conclusions can be seen in the literature. The ‘Mediterranean-style’ eating pattern has been shown to lead to the most significant reductions in HbA1C of the large scale studies performed on individuals who already had a T2D diagnosis (Evert et al., 2014). For those unaware, the Mediterranean-style diet is characterised by a high intake of fruits, vegetables, legumes, nuts, beans, cereals, grains, fish and olive oil. It is also typically low in meat and dairy products. However, it is also important to note that other studies have shown it is possible to reduce HbA1C via a variety of different calorie restricted diets which were either high in protein, low in fat or high in carbohydrate (Evert et al., 2014). That being said calorie restriction in and of itself typically improves glycaemic control, especially in overweight individuals and this may be of greater importance than the macronutrient profile and composition of the diet itself (Wheeler et al., 2010).
This brings us onto the final cornerstone, weight management. Steyn et al. (2000) found that those with the Body Mass Index (BMI) of 21-23 have the lowest risk of T2D, this is noteworthy as generally the accepted guideline for a healthy weight has been in the 18.5-24.9 range. There are however limitations to BMI, such as the fact that it fails to account for body composition. Someone with a lot of muscle mass with relatively little bodyfat may have a BMI suggestive of being overweight (25-29.9). However, you would expect them to have a lower risk than that of an individual with low muscle mass and significantly greater quantities of body fat and this is supported in the literature (Han et al., 1998). Research has consistently shown that a combination of a calorie restricted diet and regular exercise leads to greater weight loss, maintenance of weight loss and improvement of metabolic markers (Curioni and Lourenco, 2005).
In conclusion, type 2 diabetes is a particularly prevalent condition amongst Westernised countries that can lead to an assortment of other complications if not managed correctly. However, it is also especially amenable to lifestyle interventions that promote increased physical activity and improved calorie control and dietary composition which should assist in achieving a healthy body weight and composition. These interventions may be able to significantly reduce the risk of acquiring the condition or improve its management and it is worth discussing with your primary care provider.
If you are seeking to improve or maintian your health, a Personal Trainer may be the perfect solution. Find a Personal Trainer on this platform for free. Simply search for a profile near you and contact the PT direct to begin your fitness journey.
References
Church, T.S., Blair, S.N., Cocreham, S., Johannsen, N., Johnson, W., Kramer, K., Mikus, C.R., Myers, V., Nauta, M., Rodarte, R.Q. and Sparks, L., 2010. Effects of aerobic and resistance training on hemoglobin A1c levels in patients with type 2 diabetes: a randomized controlled trial. Jama, 304(20), pp.2253-2262.
Curioni, C.C. and Lourenco, P.M., 2005. Long-term weight loss after diet and exercise: a systematic review. International journal of obesity, 29(10), p.1168.
Diabetes UK, 2019. Available at: https://www.diabetes.org.uk/resources-s3/2019-02/1362B_Facts%20and%20stats%20Update%20Jan%202019_LOW%20RES_EXTERNAL.pdf [Accessed 15/03/2019]
El-Kader, S.M.A., 2011. Aerobic versus resistance exercise training in modulation of insulin resistance, adipocytokines and inflammatory cytokine levels in obese type 2 diabetic patients. Journal of Advanced Research, 2(2), pp.179-183.
Evert, A.B., Boucher, J.L., Cypress, M., Dunbar, S.A., Franz, M.J., Mayer-Davis, E.J., Neumiller, J.J., Nwankwo, R., Verdi, C.L., Urbanski, P. and Yancy, W.S., 2014. Nutrition therapy recommendations for the management of adults with diabetes. Diabetes care, 37(Supplement 1), pp.S120-S143.
Han, T.S., Feskens, E.J.M., Lean, M.E.J. and Seidell, J.C., 1998. Associations of body composition with type 2 diabetes mellitus. Diabetic Medicine, 15(2), pp.129-135.
Sigal, R.J., Kenny, G.P., Boulé, N.G., Wells, G.A., Prud'homme, D., Fortier, M., Reid, R.D., Tulloch, H., Coyle, D., Phillips, P. and Jennings, A., 2007. Effects of aerobic training, resistance training, or both on glycemic control in type 2 diabetes: a randomized trial. Annals of internal medicine, 147(6), pp.357-369.
Steyn, N.P., Mann, J., Bennett, P.H., Temple, N., Zimmet, P., Tuomilehto, J., Lindström, J. and Louheranta, A., 2004. Diet, nutrition and the prevention of type 2 diabetes. Public health nutrition, 7(1a), pp.147-165.
Umpierre, D., Ribeiro, P.A., Kramer, C.K., Leitão, C.B., Zucatti, A.T., Azevedo, M.J., Gross, J.L., Ribeiro, J.P. and Schaan, B.D., 2011. Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis. Jama, 305(17), pp.1790-1799.
Wheeler, M.L., Dunbar, S.A., Jaacks, L.M., Karmally, W., Mayer-Davis, E.J., Wylie-Rosett, J. and Yancy, W.S., 2012. Macronutrients, food groups, and eating patterns in the management of diabetes: a systematic review of the literature, 2010. Diabetes care, 35(2), pp.434-445.
Photo by Sharon McCutcheon on Unsplash
