Exercise and Type 2 Diabetes
Type 2 Diabetes is being diagnosed with increasing measure. Currently it is estimated that 285 million people or approximately 3% of the worlds population are living with the disease. Diabetes can greatly impact on an individuals health and quality of life and even decrease their lifespan considerably. The rise in the incidence of the disease has coincided with societies technological advancement. With life now requiring lower levels of movement and physical fitness we are finding a similarly sharp rise in the levels of obesity. Obesity along with physical inactivity are the main contributors to the development of Type 2 Diabetes.
What is Type 2 Diabetes?
Type 2 Diabetes is a condition related to the inability to effectively control blood glucose levels. Blood Glucose levels in the blood need to remain at precise levels. This is achieved through primarily through insulin. Insulin is a substance that enables the transport of blood glucose into the muscles. In Type 2 Diabetes blood glucose is unable to be transported into muscle and liver tissue effectively. The result is blood Glucose levels rise and begin causing havoc to your body.
Having a high blood Glucose level is called Hyperglycemia. Hyperglycemia causes damage to blood vessels and nerve cells. The damage from the elevated blood glucose leads to increases in heart disease, stroke, infection and nerve damage. (see diagram below)
Understanding Blood Glucose in the Body
Carbohydrate intake and Blood Glucose
Foods are made up of macronutrients called Carbohydrates, Fats and Proteins. These macronutrients supply the body with the energy it requires to function. When food containing Carbohydrates is consumed the carbohydrates are absorbed in the digestive track and enter the blood stream as a molecule called Glucose. Glucose level in the blood vary only slightly and total approximately 5 grams in the average person. A typical meal may contain 40-80grams of carbohydrates. These carbohydrates are absorbed faster then they are used by the body. As a result they must be stored before the blood glucose level in the blood rises above safe levels.
Glucose that is not being used by the muscles, brain or other organs is stored in the liver and muscles cells. The approximate level of Glycogen (stored glucose) found in the liver is 100 grams with the amount varying between individuals. Muscle tissue stores are estimated at between 200 - 400 grams
Muscle and Glucose use
Muscles are made up of proteins which contract in order to produce movement. Inorder for these contractions to occur a molecule called ATP is required. During contraction ATP is broken down and needs to be restored. The restoration of the ATP levels within the body is fundamental to being able to produce continued movement. This restoration requires fuels or energy from within the body. Glucose which is a simple for of carbohydrate along with stored fats are the primary source of this fuel.
Health implications of Diabetes
Diabetes causes an increased incidence of heart disease. Heart disease is the number one cause of premature death in Australia. Elevated blood glucose levels increase damage to blood vessel walls with results in an increase in atherosclerosis. Atherosclerosis is the fatty build up of plaque found in the arteries. This build up causes blockages similar to that seen in a water pipe. The result is, blood cannot reach the desired tissues, which starves the tissue of oxygen. If oxygen fails to reach the heart you'll experience what is called a heart attack, if oxygen fails to reach the brain this is called a stroke. For an article on the importance of oxygen in cells click here
Elevated Blood Glucose also causes nerve damage. Our Nerve cells are like electrical wires. They carry signals from the brain to the muscles. This is how we produce movement. They also carry feedback from the nerves in the body to the brain. This is how we feel heat, cold, pain, touch and move in a coordinated manor. Damage to nerve fibres is mostly irreparable as nerve cells grow at slow rates and in some cases they fail to recover at all. For this reason keeping blood glucose levels in the desired range is of great importance. For more information on diabetes and nerve damage see http://diabetes.niddk.nih.gov/dm/pubs/neuropathies/
Causes of Type 2 Diabetes
Diabetes in the most part is considered a lifestyle disease. This means lifestyle factor are the primarily contributer to the disease.
The mechanism of Type 2 Diabetes is still being researched. In the disease there is a decrease in insulin sensitivity. Insulin is the hormone that results in Glucose being taken from the blood and into the muscles to be later used. Having a decreased insulin sensitivity means more insulin is required to lower blood glucose levels. The exact cause of this insulin insensitivity is still debated.
Some of the contributing factors are Physical Inactivity, Excess Body Weight, High Cellular Triglyceride (fats) stores and and having a poor Aerobic Fitness level.
Physical Inactivity and Diabetes Risk
Physical inactivity is a cause of decrease insulin sensitivity. Every time you exercise there is an increase in the uptake of glucose into your cells. This can last for 24-48 hours after the exercise. Studies show that those who are physically active have a lower incidence of diabetes. A study of 87000 women over 8 years showed those who exercised vigorously once per week had .67 times the risk of developing diabetes then those who did not (1). That means a one third reduction from one exercise session a week.
A study of male physicians showed a .77 times risk for those exercise once, a .62 for those exercising 2-4 times a week and a .58 risk for those exercising 5 times per week (2). See Figure Below
A study of 7700 men found that those who exercised regularly had a .4 times risk of developing diabetes. (3)
Body Weight and Diabetes Risk
Body weight is more important then physical activity level when looking at diabetes. Diabetes is a disease related to energy storage and the heavier the individual the greater there risk of developing the disease. A study of 20000 college students looked at their level of weight gain over 27 years (4). They found that student who gain 9kg or more over this period had a 7 times greater incidence of Diabetes then those who gained only 1.5kg's. See graph for the risk associated with weight gain. Click for more Information on Weight Gain and Health
Diet and Diabetes Risk
The long term effects of diet on Type 2 Diabetes is not completely understood. Following Dietary patterns that are recommended for weight loss and will have a beneficial effect in preventing Diabetes as weight gain is the primary risk factor. Some healthy eating guidelines for weight loss are listed below
Consume fibrous foods
Eat a moderate protein intake
Eat wholegrain foods
Consume a low to moderate fat intake
Avoid excess sugar in the form of additives and excessive fruit consumption
Drink adequate water
See also Energy Balance and eating for weight loss
Excess fat intake in the diet has been shown to decrease insulin sensitivity. The high fat content may work at a cellular level to prevent glucose being used in the muscles effectively.
High sugar intakes such as those found in soft drinks, lollies, cakes, and many cereals or even high fruit intakes can lead to insulin insensitivity. Sugar is converted to fats by the liver and causes a rise in blood triglyceride. High fructose diets, the type of carbohydrate found in table sugar and fruit has been shown to decrease insulin function (5, 6)
Fructose is metabolised differently to glucose, this difference may result in excessive weight gain and cause metabolic changes at the muscle resulting in diabetes progression
Fitness Level and Diabetes Risk
Aerobic fitness level is related to the risk of developing diabetes. The higher the persons fitness level the lower their risk of developing the disease. The Multi stage Beep Test and the 2.4km Run Test are two common ways of measuring your aerobic fitness level. For more infomation on aerobic fitness and disease see aerobic fitness level, health and disease.
A 14 year follow up study of 4,747 men showed those in the highest quarter for aerobic fitness had one forth of the cases of diabetes then those in the lowest fitness level (7)
Prevention of Type 2 Diabetes
Diabetes intervention studies show large success rates for those who lose weight throughout an exercise intervention.
Interventions that increase the amount of exercise a person completes or cause a resultant weight loss will have beneficial effects for those with Type 2 Diabetes.
Preventing diabetes requires maintaining correct body weight, exercising aerobically, maintaining muscle mass through resistance or interval training and eating a diet that is not high in fat or sugars.
Step's to Prevent the Development of Type 2 Diabetes
- Eat a moderate to low fat diet -Reduce Saturated Fats and Include Omega 3’s and Monounsaturated Fats
-Reduce Sugar Intake ( no more then 1-2 sweets and 2-4 fruit serves)
-Eat vegetables and fibrous foods.
– Exercise 5 days per week for 30 minutes
-Include 2 High Intensity Training Sessions (Circuit Weight Training, Interval Running, or Sports)
-Include 2-4 30 minute Aerobic Sessions (Running, Power Walking, Swimming)
3) Maintain a Healthy Body Weight
– Use both a Waist Girth and a BMI measure.
-BMI should be between 18.5 and 25.
For Women should be less then 80 cm
For more infomation on maintaining a healthy body weight see
(1)Physical activity and incidence of non-insulin-dependent diabetes mellitus in women. Manson et al
Lancet. 1991 Sep 28;338(8770):774-8
(2) A prospective study of exercise and incidence of diabetes among US male physicians
JAMA. 1992 Jul 1;268(1):63-7.
(3) Prospective study of risk factors for development of non-insulin dependent diabetes in middle aged British men
BMJ 1995; 310:560
(4) Weight Change and Risk of Developing Type 2 Diabetes
Yuko Oguma, Howard D. Sesso, Ralph S. Paffenbarger Jr. and I-Min Lee
Obesity Research (2005) 13, 945–951; doi: 10.1038/oby.2005.109
(5) Fructose-induced in vivo insulin resistance and elevated plasma triglyceride levels in rats.
© 1989 by The American Society for Clinical Nutrition, Inc
(6) Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans
J Clin Invest. 2009 May 1; 119(5): 1322–1334.
(7) Cardiorespiratory Fitness and the Incidence of Type 2 Diabetes
Prospective study of Japanese men
Diabetes Care October 2003 vol. 26 no. 10 2918-2922
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