Diabetes Mellitus And Exercise Short Biology Essay

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The incidence of diabetes mellitus in the human population is increasing at a rapid rate.In 2000, there were an estimated 150 million cases in the world; this number is projected to increase to 370 million by 2030.

Diabetes mellitus is the leading cause of adult blindness, amputation, and major cause for renal failure, heart attacks and stroke (4).It is usually irreversible and although patients can have a normal life style, later complications are reducing life expectancy and major health costs (1).

It is strongly linked to obesity (5).

Types of diabetes mellitus

Type 1

Type 2

Causes of secondary diabetes

5% of the total diabetic cases are classified as secondary diabetes (3).

Pancreatic disease (e.g. cystic fibrosis, chronic pancreatitis, pancreatectomy, haemochromatosis, carcinoma of the pancreas) (1).

Endocrine disease (Cushing's syndrome, Acromegaly, Thyrotoxicosis, Glucagonoma)

Drug induced disease (Thiazide diuretics, corticosteroid therapy)

Insulin receptor abnormalities (congenital lipodystrophy, Acanthosis nigricans)

Genetic syndromes (Down's syndrome, Klinefeltor's syndrome, Turner's syndrome, Dystrophia mitonica)

Both forms of diabetes derive from varying degree of progressive insulin secretory failure (1).Thus some patients with immune mediated diabetes (Type 1) may not require insulin at first and many with type 2 do so.

Type 1 diabetes was previously termed as "Insulin dependent diabetes mellitus" (IDDM) (2).It is associated with insulin deficiency and requires replacement therapy. Type 2 was previously termed as "non-insulin dependent diabetes mellitus" (NIDDM) because patients can secrete some amount of insulin but exhibit insulin resistance. So initially can be treated without insulin replacement therapy. However 20% or more patients with type 2 diabetes mellitus may develop insulin deficiency, requiring replacement therapy. Therefore, IDDM and NIDDM are misnomers.

In both types of diabetes, metabolism of all foodstuffs is altered (7).The basic effect of insulin lack or resistance on glucose metabolism is, preventing the efficient uptake and utilization of glucose by most cells of the body, except brain. As a result, blood glucose concentration increases, cell utilization of glucose falls, and utilization of fats and proteins increases.

Type 1 diabetes mellitus

Due to insulin deficiency caused by autoimmune destruction or viral infection of the beta cells of the pancreatic islets (3, 7).The lack of insulin decreases the efficiency of peripheral glucose utilization and increases glucose production, rising plasma glucose concentration to 300-1200mg/100ml (7).The increased plasma glucose then has multiple effects throughout the body.

Constitute 10% of the 20 million diabetics in the US (4).This type of diabetes usually develops before the age of 40, therefore it is called, "Jevenile dibetes" (4).Unlike type 1 diabetes, patients with type 1 diabetes are not obese and usually present with diabetic ketoacidosis (8).It may develop abruptly, over a period of few days or weeks (7).


Currently, autoimmunity is considered as the major factor of type 1diabetes (8).In type 1, the islets of langerhans become infiltrated with T lymphocytes, leading to a condition called "insulitis" (4).Over a period of years, this autoimmune attack on the beta cells leads to gradual depletion of the beta cell population. Hyperglycemia, accompanied by the classical symptoms of diabetes occur only when 70-90% of beta cells have been destroyed (2).At this point, the pancreas fails to respond adequately to ingested glucose. Therefore, unable to respond to variations in circulatory fuels and to maintain a normal blood glucose level. High glucose levels may be toxic to the remaining beta cells (2).Insulin therapy is required to restore metabolic control and prevent life- threatening ketosis and acidosis (4).Eventually, type 1 is fatal unless treated with insulin (6).

Type 2 diabetes mellitus

The most common form of diabetes. Approximately 90% of the diabetic population in the US (4).More complex condition than type 1(2).In poor countries, diabetes is a disease of rich people, but in rich countries, it is a disease of poor people (1).typically, type 2 diabetes develops gradually without obvious symptoms(4).Obesity increases the risk of type 2 diabetes 80-100 fold(1). Unlike patients with type 1, type 2 diabetic patients are not absolutely dependent on insulin for life (8).


There is a combination of resistance to the actions of insulin in liver and muscle, together with impaired pancreatic beta cell function, leading to insulin deficiency (2).Insulin resistance appears first (2).It leads to elevated insulin secretion to maintain normal blood glucose levels. Then the pancreatic beta cells are unable to sustain the increased demand for insulin, leading to slowly progressive insulin deficiency. It doesn't require insulin to sustain life, but eventually, will be required to control hyperglycemia (4).

Exercise and diabetes mellitus

Diabetic patients should be strongly encouraged to take regular physical activities such as,





Approximately 30 minutes daily. Physical activity affects the metabolism of glucose and other intermediate substrates in normal subjects & in subjects with diabetes. An essential mechanism for adequate glucose supply to exercising muscles is the physiological suppression of endogenous insulin secretion. Long term effects of regular exercise are particularly advantageous for type 2 diabetic patients (11).Regular aerobic exercise reduces visceral fat mass & body weight without decreasing lean body mass, improves insulin sensitivity, glucose &blood pressure control, lipid profile & reduces cardiovascular risk(11).

Psychological gains

Less stigmatization

Improved self confidence


Healthier lifestyle attitude

Glucose metabolism during exercise

Tissue & circulating energy content provided by the 3 major fuels; fats, carbohydrates & proteins (14). However, although fat caloric support is higher, carbohydrate and especially muscle and liver glycogen represent the most important fuel in controlling glucose metabolism. At rest, blood glucose concentrations must be maintained within narrow limits. In this state, roughly half of glucose uptake occurs in the brain, while only20% is taken up by the muscle. During exercise, whole-body oxygen consumption may increase by approximately 20-fold (13).To meet its energy needs, skeletal muscle uses its own stores of glycogen & TGA, as well as FFAs are derived from the breakdown of adipose tissue, TGA & glucose released from the liver. Contracting muscles increase uptake of blood glucose, although blood glucose levels are usually maintained by glucose production via liver gluconeogenesis, glycogenolysis and mobilization of free fatty acids. Early in exercise, glycogen provides the bulk of the fuel for working muscles. As glycogen stores become depleted, muscles increase their uptake and use of circulating BG, along with FFA released from adipose tissue. To preserve neural system function, blood glucose levels are well maintained during exercise. A decrease in plasma insulin occur & the presence of glucagon necessary for the increase in hepatic glucose production during exercise. In the post-prandial state increased blood glucose causes a rise in insulin release which reduces hepatic glucose production and increases the disposal of glucose in peripheral tissue (14). During exercise there is an increase in blood flow to the working muscles to improve oxygen delivery, carbon dioxide disposal and energy substrate. Furthermore, because increased muscle energy requirements, blood glucose concentration falls leading to suppression

of insulin secretion and to activation of a variety of counter-regulatory response. During prolonged exercise, plasma glucagon & catcholamine's increases (13). Elevation in blood concentration of hormones like epinephrine, norepinephrine, glucagons and growth hormone promote activation of hepatic gluconeogenesis and glycogenolysis, adipose lipolysis hepatic and muscle glycogenolysis. Furthermore exercise induces an increased muscle glucose up-take through the insulin-independent GLUT transporter recruitment (14). Even by glycogen depletion, progressive glycogen utilization occurring during exercise determines increased GLUT-dependent glucose up-take in the post-exercise state. The metabolic and hormonal changes during exercise are characteristic for each different phase of exercise. At rest, the skeletal muscle energy sources are mainly fats and the hormonal control results from a balance between insulin and glucagon secretion. During shorter physical exercise, glycogen and blood dependent glucose is greater than fat in the working muscle; while during longer exercise fat becomes the predominant fuel. Physical training also has an important impaction in fuel metabolism. In fact, training improves the ability to use fat for energy, insulin sensitivity and skeletal muscle glycogen synthase activity. Therefore, individuals who are trained athletes utilize fuel more efficiently

than untrained subjects.

Energy fuels for exercise

Physical activity has acute & chronic effects on glucose, lipid & protein metabolism (11)


Intestinal absorption, blood stream, liver and muscle.

The basic carbohydrate for energy production readily transferred between blood stream & liver or muscle.

Glycogen (Muscle & Liver)

Storage from of carbohydrate (glucose) in muscle & liver

Feel source that is readily mobilized providing glucose.

Triglycerides (Adipose tissue& muscle)

High yield slow release from of energy storage.

Provide twice the energy per gram the carbohydrate.

Lipolysis yields FFA & glycerol.

Protein (Liver)

Minimal energy contribution through gluconeogenisis.

Physiologic Effects of exercise in Non-diabetics Vs diabetics

Hormonal changes with exercise in Non diabetics.

Insulin levels decline.

Glucagon rises.


Physical exercise and diabetes during childhood

Regular physical activity is important for the management of children & adolescents with type 1 diabetes, even before the introduction of insulin therapy (14). Current guidelines suggest the combination of regular physical exercise, insulin therapy & adequate education are important for the management of patients with type 1 diabetes. Several observational studies have shown a reduction of morbidity for vascular diseases with practiced regular exercise.

Benefits of physical exercise in patients with type 1 diabetes mellitus

Reduces serum glycemic levels before & after exercise

Improves insulin sensitivity

Reduces daily insulin dosage

Improves post -prandial glycemic peak

Improves lipid profile

Reduces weight and fat accumulation

Improves cardiovascular function

Improves blood pressure

Helps to psychological well-being and quality of life

Improves muscle rate and capacity

Risks of physical exercise in patients with type 1 diabetes




Worsening of microvascular complications

Physical exercise in patients with type 2 diabetes

 Excess body fat causes 64% of cases of diabetes in men and 77% of cases in women (6). The risk increases with age, obesity, and physical inactivity (13). Many people with type 2 diabetes can achieve blood glucose control by following a nutritious meal plan and exercise program, losing excess weight, and taking oral medications, some patients may need supplemental insulin.Reducing saturated fatty acids and trans fatty acids from the diet and  replacing them with unsaturated fatty acids, can reduce risk of type 2 diabetes (6).

Hypoglycemia developed during exercise, in patients with diabetes

Whenever you are physically active, your muscles burn glucose (12).  First, they burn the glucose, from they have stored as glycogen. As exercise continues, glucose from the blood goes into the muscles to supply their energy needs, lowering blood glucose levels. However, this shifting of glucose from the blood into the muscles doesn't end when the exercise stops. So, they take extra insulin or medication. For such individuals, more frequent blood glucose testing can help them better understand their body's response to exercise and prepare for it by adjusting medication or food intake.

Evaluation of the patient before exercise

Before beginning of exercise, the patient with diabetes mellitus should undergo a medical evaluation (13). This evaluation should be concerned for the presence of macro- and microvascular complications that may be worsened by the exercise. Identification of that will allow to minimizing risk.

Age >35 years

Type 2 diabetes of >10 years' duration

Type 1 diabetes of >15 years' duration

Presence of risk factor for coronary artery disease

Presence of microvascular disease

Autonomic neuropathy

Diaphragmatic breathing as a therapy, in control of oxidative stress in patients with type 2 diabetes mellitus

Department of biochemistry, srinivas institute of medical science & research centre, Karnataka, in India has evaluated the effect of diaphragmatic breathing on blood pressure, glycemic control and oxidative stress in patients with type 2 diabetes (9). Study involved 123 patients who were with additional diaphragmatic breathing for 3 months. It was resulted in significant reduction in body mass index, fasting and post prandial plasma glucose. They concluded it as; diaphragmatic breathing can be employed as an effective therapy in reducing the oxidative stress in patients with type 2 diabetes.

Effect of exercise intensity and duration in pregnant women at low and high risk for gestational diabetes.

R. Samuel McLaughlin Foundation of Exercise and Pregnancy Laboratory, in the University of Western Ontario have examined that exercise may influence glucose metabolism during pregnancy (9). They examined the effect of exercise intensity and duration on capillary glucose responses in pregnant women for gestational diabetes mellitus, (GDM) who have followed a modified GDM meal plan. Study entries 16-20 weeks of gestation exercise program with similar nutritional control. Exercise consisted of walking 3-4 times/week, gradually increasing time from 25 to 40 min/session. Free-living capillary glucose concentrations were measured once/week pre and post exercise. The results were as follows. Capillary glucose responses to exercise were strongly influenced by an interaction between GDM risk, exercise duration and exercise intensity It decreased after, 35 and 40 minutes of walking.

They concluded as, to achieve the best decline in CGC, pregnant women who follow a modified GDM meal plan should walk for 25 min/session at vigorous intensity or for 35-40 min/session at low intensity if they are at risk for GDM and for at least 25 minutes at either low or vigorous intensity if they are at low risk for GDM.


Preparing the individual with diabetes for a safe and enjoyable exercise program is as important as exercise itself (13). The young individual in good metabolic control can safely participate in most activities. The middle-aged and older individual with diabetes should be encouraged to be physically active. The aging process leads to a degeneration of muscles, ligaments, bones, and joints, and disuse and diabetes may exacerbate the problem. Before beginning any exercise program, the individual with diabetes should be screened thoroughly for any underlying complications.

A standard recommendation for diabetic patients, as for non-diabetic individuals, is that exercise includes a proper warm-up and cool-down period. A warm-up should consist of 5-10 min of aerobic activity (walking, cycling, etc.) at a low-intensity level. The warm-up session is to prepare the skeletal muscles, heart, and lungs for a progressive increase in exercise intensity. After a short warm-up, muscles should be gently stretched for another 5-10 min. Primarily the muscles used during the active exercise session should be stretched, but warming up all muscle groups is optimal. The active warm-up can either take place before or after stretching. After the activity session, a cool-down should be structured similarly to the warm-up. The cool-down should last about 5-10 min and gradually bring the heart rate down to its pre-exercise level.

20 Exercise safety tips for diabetic patients

Get a medical test before you start (10)

Your doctor should check your:

blood pressure

blood fat levels

Health of heart and circulatory and nervous systems

Kidney function



2. Choose exercises that fit your health

Talk to your doctor and be aware of what types of exercise are best for you. Long term diabetes cause health problems such as eye or nerve diseases which can impair exercising.

E.g. If you have lost feeling feet, it's better to swim than walking.

If you have trouble in vision, do exercise indoors.

3 .Take it easy

Don't try to do too much exercise soon. It can discourage you and can be even injured. Start simply and gradually increase how long and how hard you exercise.

4. Warm up & stretch when you start exercise

Warm up with slow exercise such as walking. This gets the heart & muscles prepared to work. After warming up, stretch gently. Stretching helps keep muscles and joints flexible. Tight muscles and joints are prone to be injury.

5. Wear right clothes

Heavy cloths are not suitable for warm weather. It causes more sweating. In the summer, wear light weight, light-colored cloths. Use sunscreen & wear a hat.

6. Check your blood glucose before exercise

If you take insulin, or other diabetic medicine, checking blood glucose before exercise is the key to avoid low blood glucose levels.

7. Timing your exercise

It's best to exercise 1-3 hours after a meal. You should avoid exercising when your insulin is peaking.

8. Be prepared to treat low blood glucose

Always carry juice, regular soft drink, glucose or another carbohydrate source. If you feel a reaction, stop, check and treat it right way.

9. Drink plenty of fluids

When you are exercising, sweating occur. It means you're losing fluid. It's important to replace fluids lost as sweat. Usually, water is the best choice. In long time exercise, it is good to have a carbohydrate contained drink.

10. Watch for low blood glucose

If you take insulin or other diabetic medicine, you may have low blood glucose levels during & after exercise. Glucose is a fuel for muscles during exercise. At the same time, exercise increases insulin action. Therefore, this both things lower blood glucose level. Get advises from your doctor to adjust insulin levels to avoid low blood glucose levels.

11. Snacking & exercise

In general, exercise lowers blood glucose levels. This can be good or bad, depending on your blood glucose level before start exercising. If you have type 1diabetes, &your pre-exercise glucose level is under 100mg/dl, exercise could lower glucose too much. Have a carbohydrate - contained .snack before beginning to exercise. Have some extra snacks to avoid lower the blood glucose during exercise.

12. Be ready to check during exercise

You should check every 30 minutes. If your blood glucose level starts to fall, stop & have a snack.

13. Check again after exercise

Specially, long-hard exercises, your blood glucose will lower for hours, after you're stopped. It's because exercise draw body glucose supply stored in the muscle & liver.

14. End exercise with cool down

Slow down gradually, until breathing becomes normal.

E.g. If you have been jogging, walk for 5 minutes to cool down.

15. Remember your feet

Check your feet after exercise. Look for blisters, warm areas, or redness.

16. Weight training

Almost everyone with diabetes, can workout with light weights. If you have eye, kidney, or blood pressure problems, you have to get advice from your doctor.

17 .Use monitoring results to learn how exercise affects your body

Exercise makes insulin work harder. When you take insulin, it also causes blood glucose reduction. If you take insulin or diabetic pills, you have to plan your exercise to avoid levels that are too low or high.

18. Know when not to exercise

If your blood glucose level is more than 300mg/dl, no matter what type of diabetes you have, it is a poor control. It is best to bring blood glucose level back before exercise. If you decide to exercise, use caution.

19. Know when to check for ketones

If you have type 1 diabetes, & your blood glucose level is 250mg/dl before exercise, stop & check for kotones, if you have moderate or large amount of ketones, don't exercise. Ketones are a sign that your insulin level is too low. Exercise cause body to make more ketones which may disrupt body's chemical balance. This can be dangerous.

20. Update your exercise plan regularly

When you're going in a regular exercise program me, you may find that there should be some changes in it. You can talk with your doctor & can change insulin doses or change exercise routine.