Worldwide, there has been an alarming increase in weight- and diet-related diseases over the past two decades. Not only rich countries, but also middle- and poor-income countries are experiencing the consequences of cheap, unhealthy, calorie-laden fast foods. This obesity pandemic is a serious threat to world health and urgent action is necessary to control and reverse it. This article briefly describes what obesity is and some of the problems it leads to.

WHAT IS OBESITY?
Overweight and obesity are defined as abnormal or excessive fat accumulation in the body that presents a risk to health.

The fat may be equally distributed throughout the body or concentrated around the stomach (leading to an apple-shaped body) or the hips and thighs (resulting in a pear-shaped body).

There are several parameters which can be used to measure a person’s level of obesity.

BODY MASS INDEX
The body mass index (BMI) is used to determine if a person’s weight is in the healthy range.

BMI provides the most useful population-level measure of overweight and obesity as it is the same for both sexes and for all ages of adults.

It is calculated by dividing one’s weight (kg) by the square of one’s height (m).
For example, if a person weighs 80kg and is 1.7m tall:

1. Multiply the height by itself 1.7 x 1.7=2.89
2. Divide the weight by this figure
3. 80 ÷ 2.89= 27.7kg/m2

Thus, 27.7 is the BMI.
Based on this calculation, the World Health Organization categorizes people as underweight, normal, overweight, obese and very obese:

However, although BMI indicates the health risk associated with being a certain weight for your height, it is just an approximate means of assessing body fat and risk to health.

MEASUREMENT OF WAIST CIRCUMFERENCE
(WAIST MEASUREMENT)
A second way of assessing one’s body size is by measuring waist circumference, which is regarded as a more accurate indicator of risk than BMI in predicting associated health risks.

The waist circumference is measured by wrapping a tape measure around the narrowest point of one’s waist (between the lower ribs and hips) while breathing out.

A waist circumference greater than 80cm (32in) for women and 94cm (37in) for men increases the risk of cardiovascular diseases, for example, heart attacks and stroke, and diabetes.

The greatest risk is for women with a waist measurement of more than 88cm (35in) and men with a waist measurement of more than 102cm (40in).

In South Asians and other ethnic groups, lower thresholds are appropriate.

Classification of obesity by waist
circumference (cm)

WAIST-HIP RATIO
A third parameter of obesity measurement has recently been introduced. It is suggested that a person’s waist-hip ratio, which measures the proportion of fat stored in the body around the waist and hips, is the best predictor of a person’s risk of a heart attack, making it a more practically useful measure than BMI.

The waist-hip ratio is calculated as follows: Measure the waist at its narrowest point; this is usually around the navel. Next, measure the hips at their widest point; most often this is around the buttocks.
It is important not to pull the measure tape tight when taking either of these measurements; let the tape rest on the skin.

Finally, divide the waist measurement by the hip measurement. The figure obtained from this calculation is the waist-hip ratio. For example, if the waist measuress 85cm (33in) and the hips are 100cm (39in), the waist-hip ratio is 85 ÷ 100 = 0.85.

For men, a ratio of more than 1.0, and for woman a ratio greater than 0.8, indicates an apple-shape body and a greater risk of health problems.

KEY FACTS
Worldwide obesity has more than doubled since 1980.

In 2008, 1.5 billion adults, aged 20 or more, were overweight. Of these over 200 million men and nearly 300 million women were obese.

65% of the world’s population live in countries where overweight and obesity kills more people than underweight.

Obesity is preventable.

FACTS ABOUT OVERWEIGHT AND OBESITY
Overweight and obesity are the fifth leading cause of deaths globally. At least 2.8 million adults die each year as a result of being overweight or obese. In addition, 44% of the diabetes burden, 23% of the ischaemic heart disease burden and between 7% and 41% of certain cancer burdens are attributable to overweight and obesity.

Stomach obesity, where weight is concentrated around the navel, is the most common type of obesity and affects 30 per cent of adult men.

Obesity and stomach obesity are rapidly increasing, especially in young people.

WHAT CAUSES OBESITY?
The fundamental cause of obesity and overweight is an energy imbalance in which more calories are consumed in the diet than expended by activity or exercise.

Obesity can be hereditary, so some people are at increased risk due to the genes they are born with.

Obesity develops due to:

• overeating (eating larger portions than you need)
• irregular meals
• eating processed or fast food
• not eating enough fruit, vegetables and unrefined carbohydrates, such as wholemeal bread and brown rice.
• lack of daily physical activity. Many people have jobs that involve sitting at a desk for most of the day, and rely heavily on their cars to get around. When it is time to relax, people tend to watch TV, or play computer games.
• Some genetic conditions can increase one’s appetite.
• Certain medical conditions can cause weight gain, such as:
• Cushing’s Syndrome (a disease of the adrenal gland)
• Hypothyroidism (an under-active thyroid gland)
• Certain medicines that can cause weight gain include:
• Corticosteroids
• Antidepressants

WHAT PROBLEMS CAN OBESITY CAUSE?
Psychologically, being overweight can affect a person’s own body image and damage self-esteem. In some cases this can cause social anxiety and depression. Common physical problems include:

• difficulty breathing
• difficulty walking or running
  
• increased sweating
  
• pain in the knees and back
  
• skin conditions, such as, acne
  
• gallstones.

The following medical conditions are also more common in obese people than in those of normal weight:

• high blood pressure
• high cholesterol
  
• diseases related to hardening of the arteries, such as, heart attack and stroke
  
• type 2 diabetes
  
• some types of cancer (endometrial, breast, and colon)
  
• musculoskeletal disorders (especially osteoarthritis – a highly disabling degenerative disease of the joints)

The risk for these non-communicable diseases increases, with the increase in BMI.

These conditions are often known as obesity-related diseases and are some of the most common causes of death before the age of 75. This is why obesity increases risk of death.