# Exercise as it relates to Disease/Effects of aerobic exercise on metabolic syndrome
## Definitions
#### What is aerobic exercise?

Aerobic exercise is physical activity of low to moderate intensity that is dependent on the presence of oxygen. Fuel sources for this energy system is primarily carbohydrates and fat.

#### What is Metabolic Syndrome?

Metabolic syndrome is a cluster of medical disorders that increase an individuals risk of CVD and Type 2 Diabetes Mellitus (T2DM). These medical disorders include:
* Excessive central obesity
* Insulin Resistance or Glucose Intolerance
* High blood pressure (systolic >130mm Hg and diastolic >85 mg Hg)
* High blood sugar levels
* High levels of triglycerides (>150 mg/dL)
* Low HDL levels (<40 mg/dL)
When a patient has multiple risk factors present the risk of CVD and T2DM increases significantly. While all of the above are risk factors central obesity and insulin resistance are recognised as the most important factors. Other risk factors include: age, genetics and hormone changes.

## Effect of aerobic exercise on Insulin Resistance and Central Obesity
#### What is central obesity and how does aerobic exercise effect it?

Central Obesity also known as abdominal obesity is the accumulation of abdominal fat resulting in an increase of waist size, an excess of this visceral fat leads to the abdomen to protrude excessively. The immediate cause of obesity is net energy imbalance: that the person comsumes more energy than is expended. Therefore, as a person increases energy expenditure via aerobic exercise, an energy balance or energy deficit is creating leading to a reduction in obesity. A person with a BMI of 30 or more is generally considered obese.
Although Metabolic Sydnrome is a combination of medical disorders, central obesity and insulin resistance is a key contributing factors, reflecting the fact the syndromes prevalence is driven by the strong relationship between waist circumference and increasing adiposity.

#### What is insulin resistance and how is it affected by aerobic exercise?

Insulin resistance is a physiological condition characterised normal amount of insulin producing a subnormal effect in muscle, adipose, and liver cells, resulting in elevated fasting glucose levels. Primary intervention strategies for insulin resistant and thus metabolic syndrome include weight reduction and increased physical activity. Insulin is produced by pancreatic β-cells and is required to prevent hyperglycaemia (high blood sugar) after meals. Insulin binds to an insulin receptor in muscle and fat cells allowing the uptake of glucose from the blood therefore, lowering blood sugar levels. However, as insulin resistance increases or the insulin receptor malfunctions, the ability of this mechanism to function is reduced preventing uptake of glucose and increasing blood glucose levels (hyperglycaemia). Aerobic exercise increases the insulin receptors sensitivity and also improves the pancreatic β-cells ability to produce insulin thus, reducing insulin resistance.

#### How does aerobic exercise affect metabolic syndrome?

There is a significant relationship between aerobic exercise, central obesity and insulin resistance. The benefits of performing aerobic exercise are beneficial as they directly reduce the risk factors of metabolic syndrome. These include:
* Reduce body fat and central obesity
* Increases insulin sensitivity
* Reduce blood pressure
* Reduce resting heart rate
* Reduce blood triglyceride levels
* Helps to increase HDL cholesterol (health cholesterol)
* Build and maintain healthy joints, muscles and bones
By reducing the effects of central obesity and insulin resistance via aerobic exercise the effects of metabolic syndrome can be significantly lowered. This also reduces the relative risk of developing CVD and type 2 diabete mellitus, two of the leading causes of mortality in Australia in 2009.

## Recommendations for aerobic exercise

Before starting any exercise program consult with your physician. The reason for this is because exercise increases blood pressure and if hypertension is already present then this can lead to aneurysms and potential ruptures. Before starting any exercise remember to warm up. 5–10 minutes of light aerobic activities before your exercise sessions is adequate. Also during exercise remember to hydrate. Water is generally the best fluid for rehydrating. Recommendations for aerobic exercise are as follows:
* Incorporate at least 150 minutes of moderately vigorous physical activity into your weekly routine. Walking is generally the easiest place to start.
       Or
* 30 minutes of moderate intensity exercise, such as walking, 5–7 days per week.
Also in addition to starting an exercise regime these dietary factors will also assist in preventing and managing metabolic syndrome.
   * Consume low GI foods
   * Increase consumption of wholegrains and
   * Include plenty of fibre in your diet
   * Eat a variety of fruits and vegetables

## Further reading

International Diabetes Foundation - Metabolic Syndrome
ESSA - Metabolic syndrome and Exercise fact sheet
Nutrition Australia - Metabolic Syndrome

## References

* ↑ McArdle, W.D., Katch, F.I. & Katch, V.L. 2006, Essentials of exercise physiology, 1st edn, Lippincott William & Wilkins.
* ↑ http://www.idf.org/webdata/docs/IDF_Meta_def_final.pdf
* ↑ McArdle, W.D., Katch, F.I. & Katch, V.L. 2006, Essentials of exercise physiology, 1st edn, Lippincott William & Wilkins.
* ↑ http://www.who.int/topics/obesity/en/
* ↑ Fauci, Anthony S. (2008). Harrison's principles of internal medicine.McGraw-Hill Medical. ISBN0-07-147692-X
* ↑ Whitney, E. & Rolfes, S.R. 2010, "Energy Balance and Body Composition" in Understanding Nutrition, eds. P. Williams & N. Rose, 12th edn, Wadsworth Cengage Learning, California, pp. 240-269
* ↑ Shulman GI. Cellular mechanisms of insulin resistance. J Clin Invest. 2000;106:171–176.
* ↑ Exercise and Physical Fitness. Doyle, A,J. (1997) Department of Kinesiology and Health at Georgia State University. http://www2.gsu.edu/~wwwfit/benefits.html
* ↑ http://abs.gov.au/ausstats/abs@.nsf/Products/B6940E9BF2695EE1CA25788400127B0A?opendocument
* ↑ http://exerciseismedicine.org.au/wp-content/uploads/2011/07/Metabolic-syndrome_full.pdf
* ↑ http://www.heart.org/HEARTORG/Conditions/More/MetabolicSyndrome/Prevention-and-Treatment-of-Metabolic-Syndrome_UCM_301927_Article.jsp
* ↑ http://www.nlm.nih.gov/medlineplus/ency/article/007290.htm
* ↑ Whitney, E. & Rolfes, S.R. 2010, "Diet and Health" in Understanding Nutrition, eds. P. Williams & N. Rose, 12th edn, Wadsworth Cengage Learning, California, pp. 604-645