Obesity as a Disease

Written by Ali Zarrouk on .

What is Obesity?

Obesity means having too much body fat. The excess fat results from the intake of calories that exceeds the number of calories spent by the body. In medical terms obesity is a condition when excess weight poses a health risk.

Obesity is determined by calculating the Body Mass Index (BMI). The BMI describes the relative weight for height. It is measured by dividing the weight in kilograms by the height in meters squared.

This index allows us to compare someone’s weight with the weight of other individuals of different heights. Using the BMI also allows us to calculate the ideal weights for individuals based on their height. The BMI strongly correlates with the total body fat content.

For example:

A person who is 170 cm tall and weighs 130 kg will have a BMI of 45 and a theoretical ideal weight of 72kg (calculated for BMI of 25). The excess weight = actual weight(130kg) – ideal weight (72kg) = 58 kg.

What is Morbid Obesity

It is a disease in which the accumulation of excess fat interferes with the functions of other organs causing serious life threatening health problems.

Classification of Obesity according to BMI



Associated Health Risk


< 19


Ideal BMI

19 - 25



25 - 30

Slight Increase




Severely Obese


Very High

Morbidly Obese


Extremely High

Super Obese


Extremely High

You can calculate your BMI using this calculator




The Obesity Epidemic

Obesity with its devastating health consequences is a worldwide problem and one of the greatest public health challenges in the twenty-first century.


Obesity Worldwide

The World Health Organization (WHO) has estimated that in 1995 200 million people worldwide were obese. This number increase to 300 million in 2000 and 400 million in 2005. By 2015 it is estimated that 700 million people will be obese and 2.3 billion will be overweight (BMI 25 to 29.9).


Obesity in Australia

According to recent estimates 67% of adult men and 52% of women are overweight. This is about 8 million Australians. About 1 in 4 adults are obese (BMI>30) and 1-2/100 are morbidly obese (BMI>40).


Causes of Obesity

Obesity is a chronic medical illness that was classified as a disease by the World Health Organization (WHO) in 1997. Obesity develops when the energy intake in food and drink is greater than the energy that is used in day-to-day activities. It is important to know that this occurs over a long period of time.

There are many factors that work together to cause this.

  1. Genetic factors
  2. Environmental and societal factors generating the ”obesogenic environment”
  3. Sedentary lifestyle
  4. Poor eating habits
  5. Cessation of smoking
  6. Psychological factors
  7. Hormonal Factors



Types of Obesity

Central versus Peripheral Obesity 


The distribution of fat in the body is as important as the total amount of fat. There are two main patterns for fat distribution:Types of Obesity


Central obesity (apple shape): the fat is carried in the abdomen. This is more common in men.


Peripheral obesity (pear shape): the fat is carried on the thighs and hips. It is more common in women.


Central obesity is associated with a higher mortality rate than is peripheral obesity. The fat inside the abdomen is more metabolically active than fat present under the skin. This causes more glucose production, type 2 diabetes, insulin resistance and hypertension. Central obesity is also associated with greater production of cholesterol leading to more atherosclerosis, coronary disease and gallstones formation.


Waist CircumferenceWaist Circumference


The waist circumference can be used as a measure of central obesity. It is measured with a measuring tape in the horizontal plane midway between the lower borders of the ribs and upper border of the iliac crest. A waist circumference measurement of >94 cm in men or  >80 cm in women is associated with increased health risks.


Waist circumference measurement is more sensitive for metabolic and cardiovascular risk screening for individuals who are overweight or borderline overweight. At higher BMI waist circumference does not appear to add more information than BMI measurement.


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