What causes people to become overweight or obese?

Quite simply we are eating too much and moving too little!

Recent statistics suggest that 7 out of 10 adults do not take enough exercise. 

Three in ten boys and four in ten girls aged 2 to 15 are not doing enough exercise.

These days, 'modern life' can mean that we are just not as active as our parents and grandparents were. For instance we watch more TV and there is so much convenience and fast food available. If we continue like this, 9 out of 10 children will grow up to have dangerous amounts of fat in their bodies. This could lead to an increase of risk to our health and possibly lead to conditions such as heart disease, type 2 diabetes and cancer.  

It is important to understand the ranges of weight which increase the risk to our health.

In adults there are two main methods of assessing overweight and obesity:
1. Body Mass Index (BMI)
2. Waist circumference.

The Body Mass Index is a tool that is used to tell how healthy a person's weight is. The BMI weight ranges, as set out by the World Health Organisation (WHO), are outlined below.

• If your BMI is less than 18.5, you are underweight for your height.
• If your BMI is between 18.5 and 24.9, you are an ideal weight for your height.
• If your BMI is between 25 and 29.9, you are over the ideal weight for your height.
• If your BMI is between 30 and 39.9, you are obese.
• If your BMI is over 40, you are very obese.

To work out if a child is overweight or obese is more complicated than adults.

Children's height and weight change at different rates at different ages. It is not possible to use simple BMI cut-off points, as used with adults, to decide whether they are overweight or obese.

Instead, a complicated calculation has to be made to children's BMI, and this calculation has to be compared to other information about how children grow at different ages in order to tell if they are overweight or obese. Different calculations also have to be made for boys and girls, and the calculations are different at different ages.

We use special growth charts to standardise children's BMI. By using these charts a child can be defined as 'overweight' and 'obese' by looking at their standardised BMI:

• BMI between 91-98%ile = Overweight
• BMI greater than 98%ile = very overweight/obese