Obesity Epidemiology

Obesity is the new epidemic worldwide especially in the developed nations. Obesity develops due to an imbalance between energy intake and expenditure such that the excess energy is stored in fat cells. These fat cells increase in number leading to several health consequences.

Excess body fat frequently results in increased risk of heart disease, diabetes, gallbladder and liver disease, arthritis and some cancers. An estimated 1.3 billion people are overweight or obese.

Causes of obesity

Among the risk factors of obesity, the prominent ones include increased intake of energy rich foods and decreased physical activity or sedentary lifestyle.

Other causes of obesity include endocrine, hypothalamic and genetic disorders.

There is a fine balance between calorie intake and expenditure that gets negatively affected by lifestyle factors such as excess dietary fat, sugar and decreased physical activity. This leads to negative alterations in the body’s physiology.

Definition of obesity

Individuals are considered obese when they weigh more than 20% above their ideal weight.

Body mass index (BMI) is calculated as weight in kilograms divided by height in meters squared. The currently accepted criteria for overweight is defined as body mass index (BMI) levels greater than 25 kg/m2 and obesity as BMI of 30 kg/m2.

Obesity in the United States

As per the reports of the National Health and Nutrition Examination Survey, 2009–2010 more than one-third of adults and almost 17% of youth were obese in 2009–2010. Compared to the earlier report in 2007-2008, there is very little change in the figures in the NHANES report.

Obesity prevalence is similar among men and women and adult men aged 60 and over were more likely to be obese than younger adults. Adult women over 60 included 42.3% obese compared with 31.9% among women aged 20–39.

With rising obesity numbers, the number of people with health conditions associated with obesity like high blood pressure, type 2 diabetes and heart disease are also on the rise. The prevalence of obesity in the United States increased during the last couple of decades of the 20th century.

In 2009–2010, 35.7% of U.S. adults were obese. This is a little over one third of the population. In 2009–2010, 16.9% of U.S. children and adolescents were obese.

Obesity prevalence was highest among teenagers than pre-school aged children. Boys tend to be more obese (18.6%) than girls (15%). Total numbers of obese in the United States include 78 million adults and about 12.5 million children and adolescents.

Worldwide trends of obesity

The highest rate of obesity and its incidence has been reported in the Pacific Islands and the lowest rates have been seen in Asia.

The rates in Europe and North American are generally high, while the rates in Africa and Middle Eastern countries are varying. The prevalence of obesity ranges from 1% in India to the Pacific Islands, where the prevalence of obesity can reach up to 80% in some regions.

According to the World Health Organization, body mass index studies cover only 86% of the worldwide population. This makes exact estimation of obesity prevalence difficult.

The WHO, however, estimates that in 2005 approximately 1.6 billion people worldwide were overweight and that at least 400 million adults were obese. This helps the WHO predict that by 2015, approximately 2.3 billion adults will be overweight and that at least 700 million will be obese.

Worldwide study of over 28 countries shows a declining trend in obesity among men in only two countries - Denmark and Saudi Arabia. Among women a decline in obesity numbers is seen in five countries including Denmark, Ireland, Saudi Arabia, Finland, and Spain.

Further Reading

Last Updated: Jan 23, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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