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Understanding Obesity, its Causes and Risks


  • Introduction
  • Classification of Obesity
  • Causes of obesity
  • Risks associated with Obesity


Obesity is a condition characterized by the abnormal accumulation of fat in the body. It’s usually classified using the Body Mass Index (BMI) however fat distribution should be considered too. Obesity is a major health issue globally with WHO attributing at least 2.8 million deaths yearly to overweight and obesity.

Obese Woman

Obesity occurs when energy intake is more than energy output. Energy intake is the amount of energy we derive from both food and drink while energy output is the energy the body expends when we are physically active and even when in rest (breathing, digestion, circulation, excretion etc.).

The prevalence of the obesity has been on a steady rise globally, both in developed and developing countries. Those most affected tend to be those that reside in urban areas. Obesity can affect people at all ages including children, but women tend to be more likely to be obese than men. In 2008, WHO reports that of the estimated number of people over the age of 20 that were obese, 205 million were men and 297 million were women.

Classification of Obesity

Various methods are used in diagnosing obesity. Some of the common ones include:
1. BMI (Body Mass Index)
2. Waist Circumference
3. Waist Hip Ratio

1. BMI (Body Mass Index)

This is the most used method to determine the body weight of an individual. It is determined by taking the body weight in kilograms divided by the weight in meters squared. BMI is used to classify the obesity of an individual. The classification is as follows:

Less than 18.5 – Underweight
18.5 – 24.9 – Normal
25.0 – 29.9 – Overweight
30.0 – 34.9 – Class 1 Obesity
35.0 – 39.9 – Class 2 Obesity
More than 40 – Morbidly obese

To calculate your BMI, please visit this page.

This measurements are only valid for adults. For children and adolescents, a BMI-for-age percentiles is used. This method calculates a child’s weight based on both age and BMI. The BMI of the child is calculated first, then plotted on a BMI-for-age percentile chart.

2. Waist circumference

Waist circumference is used to determine the fat deposition around the abdomen. For this reason it’s a good indicator of central obesity (upper-body fat) and the risk factors associated with it. Waist circumferences of more than 88cm (35 inches) in women and 102cm (40 inches) in men indicate too much belly fat and are associated with high risk of obesity-related health problems.

3. Waist to hip ratio

This is determined by taking the ratio of the waist circumference to that of the hips. A waist to hip ratio above 0.90 for males and above 0.85 for females is categorized as central obesity and is associated with higher risk of other health related problems.

Apple and Pear Body Shapes

When talking of weight, you may come across these two terms. Here’s what they mean:

a. Apple Body Shape
This is type of body shape resembles that of an apple. The defining characteristic is upper-body fat – that is, more fat in the upper region of the body (face, neck, shoulder, arms, chest, upper part of abdomen) than the lower part. This type of shape is usually referred to as Central /Abdominal Obesity and is linked with higher risk of chronic diseases like diabetes and cardiovascular diseases.

b. Pear Body Shape
In this type, the lower part of the body (thighs, hips, legs, buttocks and the abdomen) is larger than the upper part hence taking the shape of a pear. It can be found in the both sexes though it’s more common in females. Having a pear body shape is considered to not increase ones risk of chronic diseases like diabetes and cardiovascular diseases.

Causes of Obesity

1. Energy imbalance
Energy imbalance is the main cause of obesity. What this means basically is that a person consumes high amounts of energy, and in particular fats and sugar, without burning it off. Consequently, the body accumulates excess energy and stores it in the form of fat.

2. Physical Inactivity
Little to no physical activity is closely associated to Obesity. Being active uses up the energy we get from food, so if one becomes too inactive, that energy ends up being stored as fat in the body.

3. Unhealthy diet
Obesity is also contributed by poor dietary choices. This includes:

  • Diet consisting of mainly processed, packaged and fast foods that are high in both fat and sugar.
  • Overeating – eating large amounts more than you require
  • Excessive consumption of beverages that contain sugar like soft drinks
  • Excessive alcohol consumption. Alcohol contains a lot of calories which contribute to weight gain.

Unhealthy eating habits run in families. Children that learn poor eating habits from their parents may continue them into adulthood or find it hard to change them.

4. Inheritance
Obesity, in very few cases, may be caused by genetic factors inherited from parents. One such condition is the Prader-Willi syndrome, a genetic disorder which causes excessive appetite leading to extreme obesity. Genes may also affect the amount of body fat one stores and how it’s distributed and how energy from food is made and utilized by the body. Other traits such as unusually large appetites, may make losing weight problematic.

5. Health Conditions
Certain medical conditions such as an underactive thyroid gland and Cushing’s syndrome may contribute to weight gain which leads to obesity.

6. Medication
Some medicine can cause weight gain by slowing the rate of metabolism.

7. Emotional factors
Some people may eat more when stressed, depressed or when angry. This type of eating is called comfort or emotional eating and is used to make one feel happier rather than to satisfy hunger.

8. Pregnancy
Women gain weight during pregnancy to support their babies’ growth and development. After giving birth some women may find it difficult to shed this “baby weight” leading to overweight and obesity.

9. Socio-economic issues
Lacking knowledge or the means to access healthy food can lead to obesity. Lack of facilities or safe spaces for exercise may also contribute to obesity.

Risks associated with Obesity

If not managed, obesity increases one’s risk of certain health conditions. Some of these include:

It can also lead to various Psychosocial issues such as:

  • Depression
  • Low self-esteem
  • Societal discrimination
  • Loss of work days
  • Low work performance
  • Sexual Problems

Next: Prevention and Management of Obesity

Medical Disclaimer


Nutrition Point

Nutrition Point is a now defunct blog that was co-authored and maintained by the editor of this site from 2016 to 2022.

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