During the time of evolution of humans, the food supply was intermittent and for survival there was need to store energy in excess of what is required for immediate use. Fat cells did the job of storing energy, which are widely distributed in adipose tissues. The fat cells can store excess energy efficiently as triglyceride and, when needed, release stored energy as free fatty acids for use at other sites. This physiologic system developed during the time of evolution acts through endocrine and neural pathways and even can permit humans to survive starvation for as long as several months. But at present era of nutritional abundance, sedentary lifestyle, and influenced importantly by genetic endowment, this physiologic system of storing energy in adipose tissues can produce obesity and adverse health consequences due to obesity.

Obesity (and to some extent overweight) is associated with an increased risk of several health problems, such as hypertension, type-2 diabetes, dyslipidemia (which lead to heart diseases), degenerative joint disease, and some cancers and it is important for physicians to routinely identify, evaluate, and also treat patients for obesity and associated comorbid conditions appropriately. Due to the association of all the above medical conditions with obesity, it has gained importance.

What is obesity?

Obesity is presence of excess fat or adipose tissue in a human. In simple term obesity is a BMI (Body Mass Index) of 30 or higher. BMI is most commonly used diagnostic tool for obesity, although BMI is not a direct measure of fatness or adiposity e.g. a muscular lean person may be overweight or obese if only BMI is taken into account, without excess fats. BMI is equal to weight/height2 (weight in kilogram and height in meter2). In general normal BMI ranges from 18.5 to 24.9. BMI of 25-29.9 is considered as “overweight” and a BMI of 30 or more is considered obesity and BMI of more than 40 is severe obesity. Women with similar BMI have more body fat (total adipose tissue) than men. BMI below 18.5 is underweight. Click here (BMI calculator) to calculate your BMI.

Other methods that can be used in measurement or diagnosis of obesity are skin-fold thickness (anthropometry), densitometry (where body weight is measured underwater), CT, MRI, electrical impedance etc.

It is seen from large-scale epidemiologic studies that, all-cause morbidity (metabolic, cancer, and cardiovascular) begin to rise although at a slow rate when BMIs are equal to or more than 25.

Not only BMI, but distribution of adipose tissue in different anatomic locations has substantial implications for morbidity and mortality, e.g. presence of intraabdominal adipose tissue and abdominal subcutaneous fat is associated with higher morbidity and mortality than subcutaneous fat present in the buttocks and lower extremities. That is why measurement of waist-to-hip ratio of more than 0.9 in women and more than 1.0 in men is considered as abnormal. Presence of high intraabdominal adipose tissue is associated with increased incidence of insulin resistance, diabetes, hypertension, hyperlipidemia, and hyperandrogenism (in women).

How common is Obesity?

At present at least 2/3rd (more than 66%) of adult population in the United States are overweight or obese according to National Health and Nutrition Examination Surveys (NHANES) data. The number (as well as percentage) of overweight and obese population is increasing in most of the parts of the world, including developing countries and industrialized countries. Even poorest of the countries are having problems of obesity and overweight.

According to the WHO (World Health Organization) statistics overweight and obesity may soon replace as the most significant contributors to ill health, the traditional public health concerns till now, such as undernutrition and infectious diseases. The alarming fact is that the children and adolescents are becoming more obese, which indicate that the current trends will only worsen over time to become the major health problem.

The prevalence of obesity is different in different parts of the world, e.g. obesity is higher among poor socioeconomic groups in developed countries, whereas obesity is common among well to do families in developing countries.