Page 28 - Biology Form Two

Biology for Secondary Schools

The World Health Organisation (WHO) kilograms, your BMI can be calculated
recommends the normal levels of BMI as: 60 60 k
to be in the range of 18.5-25.4. BMI is (1.65) 2 = 2.7225 = 22.04 Kg m 2
calculated using the following formula:
FOR ONLINE READING ONLY
Body mass If an individual BMI falls in the range
BMI =
(Person’s height) 2 of 18.5-25.4, this is considered to be
healthy. On the other hand, if the BMI
Whereby:
is over 30, one may be at risk of
BMI = Body Mass Index in kg/m 2 diseases associated with obesity. The
Body mass = Person’s weight in kg following table shows a general guide
Person’s height = Person’s height in m
of how different values of BMI are
For example, if your height is 1.65 used to define the condition of the
metres and your body mass is 60 body.

Table 1.3: The BMI guide for adults with 20 years and above
BMI (kg/m ) Body condition
2
below 18.5 Underweight
18.5 to 25.4 Normal weight

25.5 to 29.4 Overweight or pre-obese
29.5 to 34.9 Class 1 obesity
35.0 to 39.9 Class 2 obesity

40 and above Class 3 obesity (extreme or
severe obesity

Sometimes children may suffer from obesity (childhood obesity) when their body
weight is very high in relation to their age and height. The child becomes highly
obese due to an excessive accumulation of fat in the body.

Causes of obesity
The causes of obesity include overeating, inactivity, eating high amounts of
energy foods especially fats and sugars, frequent eating, and genetic makeup.
Some people have genes that affect how foods are processed in the body.

Effects of obesity
Obesity is accompanied by several health problems, including shortness of
breath and snoring. It also increases the likelihood of conditions such as high

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