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faq about obesity

What is obesity?

The epidemic of obesity is now recognized as one of the most important public health problems facing the world today. Tragically, adult obesity is more common globally than under-nutrition. There are around 475 million obese adults with over twice that number overweight - that means around 1.5 billion adults are too fat. Over 200 million school-age children are overweight, making this generation the first predicted to have a shorter lifespan than their parents. Obesity is a medical condition described as excess body weight in the form of fat. When accumulated, this fat can lead to severe health impairments


what is the Health impact of obesity?

Obesity is an important cause of morbidity, disability and premature death (WHO, 2004). Obesity increases the risk for a wide range of chronic diseases; BMI is thought to account for about 60% of the risk of developing type 2 diabetes, over 20% of that for hypertension and coronary-heart disease, and between 10 and 30% for various cancers. Other co-morbidities include gallbladder disease, fatty liver, sleep apnoea and osteoarthritis


The disability attributable to obesity and its consequences in 2004 was calculated at over 36 million disability-adjusted life years (DALYs), due primarily to ischaemic heart disease and type 2 diabetes (WHO Global Health Risks Report, 2004). 


Obesity shortens life expectancy. In 2004, increased BMI alone was estimated to account for 2.8 million deaths, while the combined total with physical inactivity was 6.0 million (WHO Global Health Risks Report, 2004) – surpassing the excess mortality associated with tobacco, and approaching that of high blood pressure, the top risk factor for death. 


What causes obesity?

Obesity is caused by an energy imbalance; when intake of calories exceeds expenditure of calories, the surplus energy is stored as body weight. There are a multitude of ‘obesogenic’ factors contributing to the increased energy consumption and decreased energy expenditure that are responsible for obesity, including:

    •    an increased intake of energy-dense foods that are high in fat, salt and sugars but low in vitamins, minerals and other micronutrients; and

    •    a decrease in physical activity due to the increasingly sedentary nature of many forms of work, changing modes of transportation, and increasing urbanization. Social, economic, educational and cultural factors are important underlying causes of obesity, although how they inter-relate to promote or protect against the development of obesity is complex and varies considerably by country.


What About Obesity In Children?

Childhood obesity is already common, especially in westernized countries. In 2004, according to IOTF criteria, it was estimated that ~10% of children worldwide aged 5–17 years were overweight and that 2–3% were obese (Lobstein et al., 2004). Prevalence rates vary considerably between different regions and countries, from <5% in Africa and parts of Asia to >20% in Europe and >30% in the Americas and some countries in the Middle East. Becoming obese earlier in life clearly amplifies certain health risks, particularly for type 2 diabetes. 


How is obesity measured?

The most widely-used method of measuring and identifying obesity is Body Mass Index (BMI). 


BMI = weight in kg/height in m2 Overweight, or pre-obesity, is defined as a BMI of 25–29.9 kg/m2, while a BMI >30 kg/m2 defines obesity. These BMI thresholds were proposed by WHO expert reports and reflect the increasing health risk of excess weight as BMI increases above an optimal range of 21–23 kg/m2, the recommended median goal for adult Caucasian populations (WHO/NUT/NCD, 2000) 

We recommend this online BMI calculator:


Where can I read more about obesity?

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