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A.9.1 Define body mass index (BMI), overweight and obesity.

Body Mass Index (BMI)
A measurement of the relative percentages of fat and muscle mass in the human body, in which weight in kilograms is divided by height in metres and the result used as an index of obesity.
Overweight refers to increased body weight in relation to height, when compared to some standard of acceptable or desirable weight. A body mass index of more than 25 is defined as overweight by the World Health Organization. Overweight may or may not be due to increases in body fat.
Obesity is defined as an excessively high amount of body fat in relation to lean body mass. A body mass index of more than 30 is defined as obese by the World Health Organization

A.9.2 Identify values of BMI indicating overweight and obesity.

A BMI between 25 and 29.9 is considered overweight. A BMI of 30 or more is considered obese. BMI can be misleading for very muscular people or for pregnant and lactating women.

A.9.3 Explain how overweight and obesity are caused.

Obesity is a chronic disease with a strong familial component. However, it is exacerbated by low levels of physical activity combined with high energy intakes.

A.9.4 Discuss the physiological and psychological conditions associated with overweight and obesity.

Obesity increases the risk of developing conditions such as high blood pressure, diabetes (type 2), heart disease, stroke, gallbladder disease and cancer of the breast, prostate and colon. Overweight and obese persons can have low self esteem and can be victims of employment and other discrimination.

Food and cancer

A.9.5 Explain that total energy intake, especially of fat-rich foods, can be an important indirect factor in determining cancer incidence.

Food can have negative (carcinogenic) and positive (preventive) effects. Total calorie intake has a strong positive influence on cancer incidence. Foods typical of developed countries are often fat-rich and associated with breast, colon and prostate cancers. Vegetables rich in antioxidants and fibres tend to reduce cancer incidence.

A.9.6 Explain that some naturally occurring components of food have been identified as carcinogenic.

Plant alkaloids and mycotoxins have been identified as being carcinogenic.

A.9.7 Explain that cooking of food can result in the production of carcinogenic substances.

The effect of heat on food during cooking can result in the production of carcinogenic substances, including aromatic hydrocarbons (via combustion) and heterocyclic amines. Heterocyclic amines (HCAs) have been shown to cause breast, colon and prostate cancers in rats. Some epidemiological investigations positively correlate HCA intake and cancer incidence in humans.

A.9.8 Explain that some foods, for example, garlic, contain substances that can protect against cancer.

A compound in garlic has been identified by the National Cancer Institute in the United States as providing protection against cancer by slowing or preventing the growth of tumour cells. Crushing, cutting or peeling garlic and processing it into oil or powder releases an enzyme called allinase. Waiting about 15 minutes between peeling and cooking garlic allows the enzyme to work. If garlic is cooked immediately after peeling, the enzyme is inactivated.

Role of governments

A.9.9 Explain that chronic and acute food-related issues impact on health services.

Consider the impact of chronic food-related issues, for example, obesity, and acute food-related issues, for example, a food poisoning outbreak, on the health services.

A.9.10 Explain the role of governments in promoting public health.

Governments have a responsibility for ensuring public health. Food is a key issue in relation to public health. So governments have legislation to outline their role in protecting citizens and to identify statutory agencies to act in the consumers’ interest at any stage in the food production and supply chain through monitoring food safety.

A.9.11 Explain that a major role of government is to raise public awareness of food-related health issues.

Governments run campaigns to raise public awareness of food-related health issues and provide educational materials. For example, these include the health risks associated with obesity and how to treat obesity, the dangers of eating under-cooked foods, and how to ensure that food is properly cooked.


Bulleted list and italicised paragraphs are excerpted from Design Technology: guide. Cardiff Wales, UK: International Baccalaureate Organization, 2007.

Images are clickable links to its location.

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Page last modified on January 27, 2013, at 07:15 AM