Physical Activity and Exercise in Type 2 Diabetes
Physical activity (PA) and exercise are key components for effective management of type 2 diabetes. For the purposes of this article I am defining physical activity as any task resulting in an increased heart rate such as walking, gardening, manual labour or cleaning the house. Exercise on the other hand can be defined as purposeful activity such as running, swimming, attending the gym or playing sport.
Generally speaking, with physical activity or exercise, as intensity increases duration can decrease and vice versa. This is always a good rule to keep in mind. How intense or how long you are able to spend doing this will depend on your circumstances and is something I will address in the summary. Before we get to that lets examine why physical activity and exercise help diabetes control.
How PA and Exercise improve diabetes control
There are 2 main mechanisms as to how physical activity and exercise improve type 2 diabetes control. To examine this you first must understand what is driving your elevated blood glucose levels in the first place.
Type 2 diabetes is characterised by something called insulin resistance. Insulin is the hormone which tells your body’s cells to accept glucose from the blood stream. Insulin essentially opens the cell doors so glucose can enter. We therefore think of insulin as a key and the cells as doors.
In type 2 diabetes, the cell doors begin to get clogged up with fat and not as many insulin keys fit the cell locks. As a result, less glucose can enter the cell doors leaving more glucose in the blood stream. Hence why blood glucose levels increase in diabetes.
As you begin to increase your activity and fitness levels, the cells break down some of the fat clogging them up allowing the insulin keys to work once again. Therefore, you get more keys fitting the locks. We call this improved insulin sensitivity.
The second way physical activity and exercise help to lower blood glucose levels is quite ingenious. When we exercise in particular (i.e. more intense levels) our body has carrier receptors, known as GLUT-4 receptors, which can transport glucose from the blood into the cell independent of insulin. The GLUT- 4 receptors act almost like a VIP ticket for glucose molecules who do not need keys to enter the cells. This helps to reduce blood glucose levels because once the glucose enters the cells it is either used for energy or stored for energy later. The important point though is the glucose no longer remains in the blood which is where we do not want it.
Many individuals I encounter with type 2 diabetes are or have been sedentary in their day to day life. I would define sedentary as walking less than 5000 steps per day with no, little or very low intensity formal exercise.
This becomes significant because activity levels of this scale are the perfect breading ground for weight gain, the predominant factor in type 2 diabetes.
Those who lose their ability to or do not conduct regular physical activity have a very small margin of error when it comes to diet. I speak with countless patients who swear blind they do not eat large amounts. However, because of their low activity levels they are not using up the energy they are ingesting. Unfortunately, that energy has to go somewhere, and if it is not used up as fuel it will be stored as fat and thus contributes further to their diabetes progression.
This can be very frustrating for the patient. If activity levels are low then weight loss to improve their management of their type 2 diabetes must come through dietary means.
I have patients reporting a daily kilocalorie intake of 1200-1500kcal per day and still struggle to lose weight. Perhaps there is an element of under reporting going on and the evidence would suggest people typically underestimate their energy intake by approximately 20-25%. However, if they are accurate and eating very small amounts, it is very difficult to identify further areas in the diet which may induce weight loss without eating only vegetables.
Therefore, if you identify as someone who has very limited amounts of physical activity my first suggestion would be exploring where additional activity could be incorporated into your day. Perhaps this is using old cliches such as parking further away from your destination but can be as simple as pacing around when you are on the phone. Literally every little counts. Perhaps you can find more obvious gaps in your day and schedule in a daily walk to try to increase your steps.
The governments guidelines as a minimum amount of physical activity is to achieve 150 minutes per week or 30 minutes per day 5 times per week at a moderate intensity. This can also be accumulated via 10 minute blocks. Moderate intensity is defined as any activity which gets the heart beating faster and makes you feel slightly warmer. You are however still able to hold a conversion.
If the activity is vigorous and thus high intensity this can be reduced to 75 minutes per week. Here you will be unable to hold a conversation and will noticeably be out of your comfort zone.
Both these recommendations should include a combination of resistance and aerobic activity.
Keep in mind, these recommendations are the bare minimum and are for improving health and reducing the risk of lifestyle related diseases such as cardiovascular problems, diabetes, dementia, osteoporosis etc.
For weight loss, you will need to increase this to around 1 hour per day of physical activity. This tends to equate to around 10,000 steps but theres no golden rule with this. With vigorous activity the time spent doing activity can be reduced but again the guidelines focus on calorie reduction aiming to achieve somewhere between 500-600kcal reduction per day either through diet, activity or a combination of both.
It is always a good idea to quantify your activity levels and therefore using the step tracker on your smart phone or wearable device is a really good starting point.
Exercise, as mentioned for the purpose of todays article, will focus on more purposeful activities such as sport or attending the gym. This generally is performed at higher intensities than seen with day to day life activities.
There are various forms of exercise. Cardiovascular work (known commonly as cardio) is performed at moderate intensities and primarily trains the heart and cardiovascular system through repeated mechanical motions such as running or swimming.
Resistance training is concerned with strengthening exercise such as weight lifting and is good for muscular strength and bone health.
Mobility and flexibility includes activities such as yoga where the focus is on lengthening muscles.
Anaerobic exercise is very high intensity activities such as sprinting or circuits. This will take you out of your comfort zone and can cause physical distress whilst performing the activity.
In reality, most forms of exercise incorporate a combination of all these types of exercise but generally one type is predominant.
Contrary to popular belief, exercise has not been found in the literature as an effective weight loss method. This could be because for the vast majority of people exercise takes up a very small proportion of the week leaving many more hours to undo the good work. It may also be because exercise lures people into a false sense of security with their dietary choices believing they can eat more than they have actually expended during exercise.
Whatever the reason, the results of inactivity is something I see transparently in practice very regularly. How much you need to do varies from individual to individual because each different person will perform differing amounts of exercise, at different intensities at different frequencies. For example, someone running 5 times per week with a running club, at varying intensities will likely see very different results from someone attending a Zumba class twice weekly.
Conducting regular physical activity is without doubt a beneficial endeavour. Those who do participate regularly at good intensities do see results and improve their diabetes control. We shouldn’t also forget the health benefits associated with regular exercise.
An ideal would be to combine regular physical activity with exercise but in todays modern society many jobs make this difficult.
I would advise looking at your own circumstances and devising a plan of how you can get active. If you have an office job and spend time commuting to work, chances are you will not achieve the necessary amount of intensity through physical activity alone to make a significant difference to your weight or diabetes control. In this instance, more formal exercise may be the route for you because it will be higher intensity and lower duration.
If you are more elderly and/or formal exercise is no longer an option for you, a more gentle approach such as prolonged walks might be a more realistic option for you.
When it comes to physical activity and exercise the general rule is the more you can achieve the better. Try not to overcompensate with your food intake if exercising. Yes you may find your appetite increases following activity but do not add additional items to your diet such as dessert because you have increased your activity levels.
Remember, the less active you are the more changes will need to come through dietary means to improve your type 2 diabetes control but this can be difficult to achieve if you are sedentary.