By Dr Ananya Mandal, MD
Obesity usually is caused by the underlying pathology of accumulation of excess body fat. It impairs health to a great extent especially by raising the risk of other chronic illnesses such as heart disease and diabetes. Obesity is defined as a Body Mass Index (BMI) exceeding 30 kg/m2.
Obesity is one of the most prevalent disorders of developed countries, and its incidence is increasing rapidly. In England for example obesity rose between 13.2% to 23.6% in men and 16.4% to 23.8% in women between 1993 and 2004. In the United States the numbers rose from 23% in 1990 to 31% in 2000. In both countries present figures are nearly one third of the total population.
Obesity and risk of disease
Central obesity as well as obesity in general is associated with physiological changes that may cause the development of diseases like high blood pressure, heart disease, high blood cholesterol and type 2 diabetes.
Obesity also raises the risk of fatty liver disease, gall bladder disease, osteoarthritis and certain cancers. It is estimated that the cost of treating obesity related diseases contributes 2–7% of total national health care costs in developed countries.
Diabetes is defined as the inability of the body to regulate and control the blood sugar levels. Persistent and long term raised blood sugar is associated with damage to blood vessels, nerves and several organs.
Incidence of obesity and type 2 diabetes
As the incidence of obesity rises rapidly, so does that of Type 2 diabetes. In 2000 for example the incidence of diabetes worldwide was 171 million. Studies estimate that these numbers are set to rise to 366 million by 2030 according to the World Health Organization.
Type 2 diabetes is on a major rise especially in developing countries along with the developed countries. This is probably because of the switching of the developing country populations to a more affluent lifestyle of poor and unhealthy diet accompanied by lack of physical activity.
Diabetes mellitus and obesity
Diabetes mellitus and obesity have a complex relationship. There is a strong association of type 2 diabetes with obesity. Obesity is one of the major risk factors for type 2 diabetes.
Further obesity is a precursor of type 2 diabetes with insulin resistance. Insulin is a hormone produced by the pancreas in the body to regulate and bring down the blood sugar levels.
In obese individuals with type 2 diabetes, the amount of insulin produced in the body may be normal but this may not meet the requirements of the body. Thus the blood sugar remains elevated. This is termed insulin resistance.
Insulin resistance is the hallmark of type 2 diabetes seen among obese individuals.
Treatment and prevention of type 2 diabetes by reduction of obesity
For treatment and prevention of Type 2 diabetes, reduction of obesity is a key goal all over the world. The main aims for treating both obesity and diabetes are to:-
reduce caloric intake
increase physical activity
Newly diagnosed cases of diabetes and obesity are always treated in this way before adding medications to bring down blood sugar.
Association between fats and diabetes
Free fatty acids are the most important source of energy for liver, kidney and muscles and help produce triglycerides in the liver. In periods of prolonged fasting, the fatty acids replace glucose as source of energy. These free fatty acids are stored in the body in the form of triglycerides in the white adipose tissue.
When fasting these, free fatty acids are released from triglycerides by the process of lipolysis or fat breakdown. Once in the muscles these fatty acids are oxidized to release energy.
Insulin is one of the main hormones that regulated the breakdown of fats into usable glucose. When there is insulin resistance there is lack of this regulation and a consequent rise in free fatty acid levels. This is the characteristic feature of type 2 diabetes mellitus.
Obesity and hormones
Further obesity changes the hormones secreted by adipose tissue or fat tissues. The major hormones that are affected are the adipokines. In the obese state, adipose tissue secretes proportionally more adipokines that cause insulin resistance.
Furthermore, obesity is associated with an increase in secretion of chemokines by the adipose tissues. This leads to activation of inflammatory cells like macrophages. Activated macrophages produce cytokines that can decrease insulin sensitivity and increase insulin resistance.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)
Last Updated: Apr 8, 2013