The Body Mass (BMI) is a conventionally accepted standard for evaluating the degree of overweight by health practitioners; this puts everyone at different categories of risk depending on the excessiveness of weight gained. Following the BMI classification, individuals with BMI less than 18 are underweight. A healthy weight is considered to be from between 18-25; while from 25-30 is overweight, over 30 is excessive overweight. Values over 35 is obese while those higher than 40 are termed morbid obesity.

Although, 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. However, it should be considered a rough guide because it may not correspond to the same degree of fatness in different individuals.

In March 2013, WHO statistics revealed that 2.8 million people die yearly as a result of overweight/obesity related complications.

Being overweight/obese is a major risk factor for a number of chronic and degenerative diseases like diabetes, hypertension, cardiovascular diseases and cancers. Expectant mothers are also at a high risk while it equally plays a major role in infertility, male impotency, stroke, arthritis, physical alertness, and surgical procedures. The social and psychological effect of being obese, in most cases begins with a feeling of low self esteem, withdrawal and then graduates into different stages of depression.

Key facts

• 1. Worldwide obesity has more than doubled since 1980.
• 2. In 2014, more than 1.9 billion adults, 18 years and older, were overweight. Of these over 600 million were obese.
• 3. 39% of adults aged 18 years and over were overweight in 2014, and 13% were obese.
• 4. Most of the world's populations live in countries where overweight and obesity kills more people than underweight.
• 5. 42 million children under the age of 5 were overweight or obese in 2013.
• 6. Obesity is preventable.

Some recent WHO global estimates follow

• 1. In 2014, more than 1.9 billion adults, 18 years and older, were overweight. Of these over 600 million were obese.
• 2. Overall, about 13% of the world’s adult population (11% of men and 15% of women) was obese in 2014.
• 3. In 2014, 39% of adults aged 18 years and over (38% of men and 40% of women) were overweight.
• 4. The worldwide prevalence of obesity more than doubled between 1980 and 2014.

In 2013, 42 million children under the age of 5 were overweight or obese. Once considered a high-income country problem, overweight and obesity are now on the rise in low- and middle-income countries, particularly in urban settings. In developing countries with emerging economies (classified by the World Bank as lower- and middle-income countries) the rate of increase of childhood overweight and obesity has been more than 30% higher than that of developed countries.

Overweight and obesity are linked to more deaths worldwide than underweight. Most of the world's population live in countries where overweight and obesity kill more people than underweight (this includes all high-income and most middle-income countries).

What causes obesity and overweight?

• 1. An increased intake of energy-dense foods that are high in fat; and
• 2. An increase in physical inactivity due to the increasingly sedentary nature of many forms of work, changing modes of transportation, and increasing urbanization.

What are common health consequences of overweight and obesity?

• 1. Cardiovascular diseases (mainly heart disease and stroke), which were the leading cause of death in 2012;
• 2. Diabetes;
• 3. Musculoskeletal disorders (especially osteoarthritis - a highly disabling degenerative disease of the joints);
• 4. Some cancers (endometrial, breast, and colon).