Frequently Asked Questions

What does BMI stand for?

BMI stands for Body Mass Index. When used for children, Body Mass Index takes into account age, gender, height and weight.

How is BMI calculated?

BMI is calculated by dividing a person's weight (in kilograms) by the square of their height (in metres).

Is BMI different for children and adults?

BMI is calculated for children and adults in the same way; however the results should be interpreted differently. For adults, a BMI of between 20 and 25 is considered 'healthy'. There is no generic 'healthy' range for children as they are continually growing; therefore age and gender also needs to be considered.

What is used to decide whether a BMI is too high?

In England, the British 1990 (UK90) growth reference charts are used to determine the growth status of an individual child. The age and gender specific growth centiles (zones) are based on 17 separate surveys which together produced a large sample of 37,700 children.

Is BMI the best measure of health in children?

BMI can give an indication as to whether a child's weight is increasing faster than expected and at a faster rate than their height. The result should be considered alongside other information about a child's lifestyle. A child with a slightly high BMI can still be healthy however there may be a concern that excess weight may lead to serious health problems at some stage. Similarly a child with a low BMI can be healthy yet may need to be monitored to ensure that sufficient nutrients are consumed.

Why does my child's result say 'Above recommended weight' when he looks fine?

Research tells us that parents find it almost impossible to visually assess whether their child's weight is increasing too quickly. Friends and family may also find it difficult to assess a child's weight status. An indicator is the size of clothes that a child wears (in years of age), whether this corresponds with their actual age and whether their clothes need to be altered in length.

Can a child be above recommended weight if they do lots of exercise?

Children can be extremely active yet still have a high BMI. This suggests that even though a child is burning off lots of energy there is still an energy imbalance, that is, they are still consuming more than they need.

Should I be concerned if my child's result is not in the green zone?

If your child plots in the orange or yellow zone it might be useful to look at your child's lifestyle in terms of food, drink and exercise and consider potantial changes. Most people have changes that could be made, whether it's an activity increase, sugary drink swap or portion control. However, if you are concerned you may choose to visit your GP to discuss this further.

Is my child 'obese'?

Obese is a medical term and not one that is used to feedback to parents on CHAMP. A child would be medically obese if they plotted on or above the 98th centile line on the BMI chart.

Does my child need to lose weight?

Only in very exceptional circumstances do primary aged children need to lose weight and this must be under the supervision of a nutritional expert. If a child is plotting high on the BMI chart, then it is generally advisable to monitor their weight at home and aim for a slowdown in weight increase or for weight stability. The calculator on CHAMP can be used to re-check a child’s BMI at home.

My child is tall for their age - does this make a difference?

BMI takes into account a child's height and so does not make a difference when plotting on the BMI chart.

Why is my child's result different if I plot the measurements using an older age?

Children grow at different rates through childhood and have slightly different body composition according to their age. Plotting a younger child's results using an older age are likely to produce a different result.

What happens to my data?

All data is stored securely by Manchester University NHS Foundation Trust (MFT) and may be added to your child’s health record and therefore accessible by relevant health professionals.

No individual measurements are given to school staff or other children. Please contact us if you wish to remove your measurements from your health record. Also anonymous data may be shared for analysis, research and service planning purposes.

You may opt out if you wish, without detriment to the care being provided. Please contact us to do so.

We also share your email address with our third party email provider ‘SendinBlue’ so that we can email you with information and advice. To unsubscribe from this service simply click on the unsubscribe link contained within any email that you receive from us.

Illustration of parents and children