Weight gain that is abnormal or excessive and poses a risk to health is what is meant by the terms “overweight” and “obesity.” Overweight is defined as a body mass index (BMI) of 25, and obesity as a BMI of greater than 30. According to the global burden of illness, the problem has reached epidemic proportions, with over 4 million people dying annually as a result of being overweight or obese in 2017. The prevalence of overweight and obesity in both adults and children is rising. Globally, the incidence of overweight or obesity among children and adolescents aged 5 to 19 more than quadrupled from 4% to 18% between 1975 and 2016.


In every continent, with the exception of sub-Saharan Africa and Asia, more people are fat than underweight today, which is one side of the double burden of malnutrition. Overweight and obesity, formerly thought to be a problem exclusively in high-income nations, are now sharply increasing in low- and middle-income nations, especially in metropolitan areas. Children who are overweight or obese make up the majority of the population in developing nations, where the pace of rise has been more than 30% greater than in industrialized nations.


Obesity is commonly understood to be a significant buildup of body fat that may have negative effects on health. Based on a person’s body mass index (BMI), which is a ratio of their weight in kilograms to the square of their height in meters, medical organizations frequently categories persons as obese. The World Health Organization (WHO) defines “obese” for adults as having a BMI of 30 or higher and “overweight” as having a BMI of 25 or higher. A BMI of 30 to 35 is classified as class 1 obesity, a BMI of 35 to 40 as class 2, and a BMI of 40 or more as class 3 obesity by the U.S. Centers for Disease Control and Prevention (CDC).

Measures of childhood obesity take age, height, and weight into account. The WHO defines obesity in children aged 5 to 19 years.

Specific organizations have made some changes to the WHO definitions. The surgical literature divides class II and class III obesity, or only class III obesity, into further categories, the values of which are currently up for debate.

  • Any BMI ≥ 35 or 40 kg/m2 is severe obesity.
  • A BMI of ≥ 35 kg/m2 and experiencing obesity-related health conditions or ≥ 40 or 45 kg/m2 is morbid obesity.
  • A BMI of ≥ 45 or 50 kg/m2 is super obesity.

Some countries have changed their definitions of obesity because Asian populations experience negative health effects at lower BMIs than Caucasians do. For example, China uses a BMI of greater than 28 kg/m2, while Japan uses a BMI of greater than 25 kg/m2.

The body fat percentage (BF%), which is the ratio of a person’s total weight in fat to their body weight, is the preferred obesity measure in academic circles, while BMI is only used as a rough approximation of BF%. In general, levels above 32% for women and 25% for males are regarded as being obese. Individual differences in lean body mass, particularly muscular mass, are ignored by the BMI. Despite having little fat, those who engage in strenuous physical activity or sports may have high BMI readings. For instance, according to the BMI measure, more than half of all NFL players are categorized as “obese” (BMI 30), and 1 in 4 are categorized as “extremely obese” (BMI 35). Their average body fat level, at 14%, is, nevertheless, well within what is regarded as a healthy range. Similar to how athletes may be classified as “severely obese” or “very severely obese” based on their BMI, many Sumo wrestlers who have less than 25% body fat are not considered obese.

What are obesity and overweight

The definitions of overweight and obesity include abnormal or excessive fat buildup that might harm one’s health.
Body mass index (BMI) is a straightforward measure of weight in relation to height that is frequently used to categories adult overweight and obesity. It is determined by dividing the individual’s weight in kilograms by the square of his or her height in meters (kg/m2).


For adults, WHO defines overweight and obesity as follows:

  • overweight is a BMI greater than or equal to 25; and
  • obesity is a BMI greater than or equal to 30

Due to its universal applicability to adults of all sexes and ages, BMI serves as the most useful population-level indicator of overweight and obesity. However, because it might not correspond to the same level of fatness in different people, it should only be used as a rough guide.

Age must be taken into account when defining overweight and obesity in children.

Children under 5 years of age

For children under 5 years of age:

  • overweight is weight-for-height greater than 2 standard deviations above WHO Child Growth Standards median; and
  • obesity is weight-for-height greater than 3 standard deviations above the WHO Child Growth Standards median.

Children aged between 5–19 years

Overweight and obesity are defined as follows for children aged between 5–19 years:

  • overweight is BMI-for-age greater than 1 standard deviation above the WHO Growth Reference median; and
  • obesity is greater than 2 standard deviations above the WHO Growth Reference median.

Facts about overweight and obesity

Some recent WHO global estimates follow.

  • Over 1.9 billion adults who were 18 years of age and older were overweight in 2016. Over 650 million of these adults were obese.
  • 39% of adults over the age of 18 in 2016 were overweight (40 % of women and 39% of males).
  • In 2016, 11% of men and 15% of women in the adult population worldwide were obese.
  • Between 1975 and 2016, the prevalence of obesity nearly quadrupled globally.

A whopping 38.2 million kids under the age of five were reportedly overweight or obese in 2019. Overweight and obesity, formerly thought to be an issue only in high-income nations, are increasingly becoming more prevalent in low- and middle-income nations, especially in metropolitan areas. Since 2000, there has been a nearly 24% increase in the proportion of under-5-year-old overweight children in Africa. In 2019, Asia was home to over half of the world’s young overweight or obese children.

In 2016, there were approximately 340 million overweight or obese kids and teenagers between the ages of 5 and 19.

From barely 4% in 1975 to slightly over 18% in 2016, the prevalence of overweight and obesity among children and adolescents aged 5 to 19 has increased considerably. Both boys and girls have seen an increase in weight, with 18% of girls and 19% of boys being overweight in 2016.

In 1975, fewer than 1% of children and teenagers aged 5 to 19 were obese; by 2016, this number has increased to more than 124 million (6% of females and 8% of boys).

More fatalities than underweight are associated with being overweight or obese worldwide. In every region of the world with the exception of some areas of sub-Saharan Africa and Asia, there are more fat individuals than underweight people.

What causes obesity and overweight?

Obesity and overweight are primarily caused by an imbalance in energy between calories ingested and calories burned. Around the world, there have been:

  • an increase in the consumption of fattening and sugary foods that are rich in energy, as well as an increase in physical inactivity because of the changing modes of transportation, growing urbanization, and the sedentary nature of many occupations.

A lack of supportive policies in areas like health, agriculture, transportation, urban planning, environment, food processing, distribution, marketing, and education often leads to environmental and societal changes that affect dietary and physical activity patterns.

Common Health Consequences of Overweight and Obesity

Increased BMI is a significant risk factor for noncommunicable illnesses like:

  • cardiovascular diseases (mainly heart disease and stroke), which were the leading cause of death in 2012;
  • diabetes;
  • musculoskeletal disorders (especially osteoarthritis – a highly disabling degenerative disease of the joints);
  • some cancers (including endometrial, breast, ovarian, prostate, liver, gallbladder, kidney, and colon).

As BMI rises, the risk for these noncommunicable diseases also rises.

Common Health Consequences of Overweight and Obesity

Childhood obesity increases the risk of grownup obesity, untimely mortality, and disability. However, obese children also experience breathing issues, an increased risk of fractures, hypertension, early indicators of cardiovascular disease, insulin resistance, and psychological effects in addition to their increased future risks.

Facing a Double Burden of Malnutrition

The “double burden” of malnutrition is currently being felt by many low- and middle-income nations.

  • While these countries continue to deal with the problems of infectious diseases and undernutrition, they are also experiencing a rapid upsurge in noncommunicable disease risk factors such as obesity and overweight, particularly in urban settings.
  • It is not uncommon to find undernutrition and obesity co-existing within the same country, the same community and the same household.

Children in low- and middle-income nations are more susceptible to malnutrition during pregnancy, as a newborn, and as a young kid. These kids are also exposed to diets that are heavy in fat, sugar, salt, and energy, but low in micronutrients. These foods are typically less expensive, but their nutritional value is also reduced. These eating habits, coupled with a decline in physical activity, cause a dramatic rise in childhood obesity while undernutrition problems go unresolved.

How can overweight and obesity be reduced?

Obesity and overweight are mostly avoidable, as are the noncommunicable illnesses that they are associated with. Healthy eating and regular exercise are the simplest choices to make (the options that are most accessible, available, and cheap), which prevents overweight and obesity. Supportive settings and communities are essential in influencing people’s choices.

At the individual level, people can:

  • limit energy intake from total fats and sugars;
  • increase consumption of fruit and vegetables, as well as legumes, whole grains and nuts; and
  • engage in regular physical activity (60 minutes a day for children and 150 minutes spread through the week for adults).

Only in communities where individuals have access to a healthy way of life can individual responsibility be fully felt. At the societal level, it is crucial to encourage people to heed the aforementioned advice by persistently implementing population-based, evidence-based policies that make regular physical activity and healthier eating options readily available, affordable, and easily accessible to everyone, especially the poorest people. An illustration of such a measure is a tax on beverages with added sugar.

The food business may significantly contribute to the promotion of a healthy diet by:

  • reducing the fat, sugar and salt content of processed foods;
  • ensuring that healthy and nutritious choices are available and affordable to all consumers;
  • restricting marketing of foods high in sugars, salt and fats, especially those foods aimed at children and teenagers; and
  • ensuring the availability of healthy food choices and supporting regular physical activity practice in the workplace.


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