Obesity is a condition that is defined by a range of physical factors, the most important of which is the excess amount of fat stored within the body of any person. Obesity is the most extreme form of excess weight; the greater the excess, the more limited the person will be in physical capabilities, and the more significant the corresponding strains placed on the bodily processes such as the cardiovascular system. Obesity carries with it an inevitably greater risk that the person will develop and die from a serious disease.
One of the most common physical consequences of obesity is the development of insulin resistance. Insulin is a hormone produced by the pancreas as a part of the body's mechanism of processing and regulating the level of glucose in the bloodstream. After food has been consumed, insulin acts as a chemical-signaling device to maintain glucose levels at a steady rate. The countervailing hormone to insulin is glucagon, which will signal the body to correct a glucose level that is too low through the release of glucose, stored as glycogen, from the liver.
In a synthetic form, insulin is used as a medication, injected directly into the bloodstream of persons who suffer from type 1 diabetes (also known as juvenile diabetes), the disease caused when the body is not able to produce any, or enough, insulin. These insulin injections are essential to the survival of patients in these circumstances. The discovery of synthetic insulin by Frederick Banting (1891–1941) and Charles Best (1899–;1978) of the University of Toronto in 1921 is regarded as one of the great advances in the history of medical science. Insulin is essential to the health of millions of diabetics throughout the world.
Insulin resistance arises where the ability of insulin to regulate and to signal changes to glucose levels in the blood is decreased. When the cells of the body become insulin resistant, the message that should otherwise be conveyed to the cells by the presence of insulin is not the subject of an immediate response from the body. When the cells do not respond to the insulin signal for glucose balance, ever-increasing amounts of insulin are produced in the pancreas, which treats the lack of cellular response to the presence of insulin to mean that more insulin is required. Insulin resistance is a form of biological misinformationthe body believes that it must increase the amount of glucose. When the insulin message is finally acted on by the cells, there is a flood of glucose into the cells from the bloodstream, which creates a condition known as a hypoglycemic reaction, more commonly stated as low blood sugar. Insulin resistance produces a cycle of repeated spikes in blood sugar level will eventually exact a toll on the pancreas and its ability to produce insulin. When the body is not protected by its blood sugar-leveling mechanism, it is vulnerable to the opposite condition, hyperglycemia, excessive blood sugar. When insulin resistance is untreated, death is a likely event.
The risk of becoming diabetic, or insulin resistant, is genetic in origin for some persons, creating a greater likelihood of becoming diabetic no matter what environmental factors are involved, including diet and lifestyle. There is, however, no question that all persons who are overweight or obese are at far greater risk. As an obese person gains excessive weight, they subject their pancreas to long-term stresses in insulin production.
Insulin resistance has other serious consequences, as it will often lead to the progressive illness known as the metabolic syndrome, which is the combination of a series of distinct physical conditions. Each component of the metabolic syndrome is potentially dangerous to human health when present alone: type 2 diabetes (diabetes mellitus), hypertension (high blood pressure), hyperlipidimedia (the production of excessive levels of low density lipoproteins, a harmful cholesterol that causes plaque to form inside the blood vessels, which causes a narrowing and the potential for restricted blood flow), and obesity, characterized by the presence of a "beer belly," the presence of fat deposits that are more pronounced along the abdomen.
The onset of type 2 diabetes creates a further series of health risks. Type 2 diabetics have a proven greater risk of cardiovascular disease, renal (kidney) failure, and the risk of various infections, particularly when the skin is cut or a sore develops. Type 2 diabetes can often be controlled through a comprehensive program of proper diet (with careful attention to the amount of carbohydrates consumed), weight management, and an exercise program, coupled with medication, chiefly insulin or those of the thiazolidinedione type. The diet formulations required for persons with insulin resistance will involve a consideration of the glycemic index, a food-ranking system that assists in determining which types of food are absorbed more slowly and steadily into the body, and which are absorbed quickly. As glucose levels in the blood are never constant, due to variable impacts of environment, exercise, illness, stress, or similar factors, an effective program to counter insulin resistance must be flexible and responsive to the effect of these variables.
Insulin resistance is an irreversible and progressive condition; once the body's cells do not respond to insulin, the glucose levels must be controlled through human intervention and monitoring. In obese persons, insulin resistance is another stressor on the body that heightens the considerable risk of early mortality.