On World Obesity Day- 11 October 2017, the World Health Organization (WHO) has released the results of a new study investigating global trends in underweight, overweight and obesity. It has also updated its fact sheet on overweight and obesity.
Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health.
Body mass index (BMI) is a simple index of weight-for-height that is commonly used to classify overweight and obesity in adults. It is defined as a person’s weight in kilograms divided by the square of his 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.
For children, age needs to be considered when defining overweight and obesity.
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.
Obesity rates in the world’s children and adolescents increased from less than 1% (equivalent to five million girls and six million boys) in 1975 to nearly 6% in girls (50 million) and nearly 8% in boys (74 million) in 2016.
Combined, the number of obese five to 19 year olds rose more than tenfold globally, from 11 million in 1975 to 124 million in 2016. An additional 213 million were overweight in 2016 but fell below the threshold for obesity.
In 2016, there were 50 million girls and 74 million boys with obesity in the world, while the global number of moderately or severely underweight girls and boys was 75 million and 117 million respectively.
Over 340 million children and adolescents aged 5-19 were overweight or obese in 2016.
The number of obese adults increased from 100 million in 1975 (69 million women, 31 million men) to 671 million in 2016 (390 million women, 281 million men). Another 1.3 billion adults were overweight, but fell below the threshold for obesity.
In 2016, more than 1.9 billion adults aged 18 years and older were overweight. Of these over 650 million adults were obese.
In 2016, 39% of adults aged 18 years and over (39% of men and 40% of women) were overweight.
Overall, about 13% of the world’s adult population (11% of men and 15% of women) were obese in 2016.
If post-2000 trends continue, global levels of child and adolescent obesity will surpass those for moderately and severely underweight youth from the same age group by 2022. In 2016, the global number of moderately or severely underweight girls and boys was 75 million and 117 million respectively.
Nevertheless, the large number of moderately or severely underweight children and adolescents in 2016 (75 million girls and 117 million boys) still represents a major public health challenge, especially in the poorest parts of the world. This reflects the threat posed by malnutrition in all its forms, with there being underweight and overweight young people living in the same communities.
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 countries are more vulnerable to inadequate pre-natal, infant, and young child nutrition. At the same time, these children are exposed to high-fat, high-sugar, high-salt, energy-dense, and micronutrient-poor foods, which tend to be lower in cost but also lower in nutrient quality. These dietary patterns, in conjunction with lower levels of physical activity, result in sharp increases in childhood obesity while undernutrition issues remain unsolved.
Children and adolescents have rapidly transitioned from mostly underweight to mostly overweight in many middle-income countries, including in East Asia, Latin America and the Caribbean. The authors say this could reflect an increase in the consumption of energy-dense foods, especially highly processed carbohydrates, which lead to weight gain and poor lifelong health outcomes.
In Africa, the number of overweight children under 5 has increased by nearly 50 per cent since 2000. Nearly half of the children under 5 who were overweight or obese in 2016 lived in Asia.
The rise in childhood and adolescent obesity rates in low and middle income countries, especially in Asia, has recently accelerated. On the other hand, the rise in childhood and adolescent obesity in high income countries has slowed and plateaued.
The areas of the world with the largest increase in the number of obese children and adolescents were East Asia, the high-income English-speaking region, and the Middle East and North Africa.
Among high-income countries, the United States of America had the highest obesity rates for girls and boys.
The largest rise in BMI of children and adolescents during the four decades was in Polynesia and Micronesia for both boys and girls, and in central Latin America for girls. The smallest rise in the BMI of children and adolescents during the four decades covered by the study was seen in Eastern Europe.
India had the highest prevalence of moderate and severe underweight throughout these four decades (24.4% of girls and 39.3% of boys were moderately or severely underweight in 1975, and 22.7% and 30.7% in 2016). 97 million of the world’s moderately or severely underweight children and adolescents lived in India in 2016.
Consequences of raised BMI
Raised BMI is a major risk factor for noncommunicable diseases such as:
- cardiovascular diseases (mainly heart disease and stroke), which were the leading cause of death in 2012;
- musculoskeletal disorders (especially osteoarthritis – a highly disabling degenerative disease of the joints);
- some cancers (including endometrial, breast, ovarian, prostate, liver, gallbladder, kidney, and colon).
The risk for these noncommunicable diseases increases, with increases in BMI.
Childhood obesity is associated with a higher chance of obesity, premature death and disability in adulthood. But in addition to increased future risks, obese children experience breathing difficulties, increased risk of fractures, hypertension, early markers of cardiovascular disease, insulin resistance and psychological effects.
Prevention of overweight and obesity
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).
Individual responsibility can only have its full effect where people have access to a healthy lifestyle.
The food industry can play a significant role in promoting healthy diets 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.
Countries should aim particularly to reduce consumption of cheap, ultra-processed, calorie dense, nutrient poor foods. They should also reduce the time children spend on screen-based and sedentary leisure activities by promoting greater participation in physical activity through active recreation and sports.
Link to the WHO news release:
Link to the article in The Lancet (English) [PDF]:
Link to data visualizations for child and adolescent BMI:
Link to data visualizations for adult BMI:
Link to news release by Commission on Ending Childhood Obesity:
Link to Executive Summary of Implementation Plan by Commission on Ending Childhood Obesity (English) [PDF]:
Link to WHO’s updated fact sheet on overweight and obesity:
Link to World Obesity Day website:
Link to infographics on obesity (multiple languages):