HealthInfo West Coast-Te Tai Poutini
Finding out if my child is a healthy weight
He aha te taumaha hauora o tāu tamaiti?
Tamariki (children) come in different shapes and sizes – big, tall, small and short. There is a wide range of healthy shapes and sizes.
Tamariki who stay a healthy weight tend to be fitter, healthier, better able to learn and more self-confident. They are also much less likely to have health problems later in life.
The body mass index (BMI) is a way to find out if your tamaiti (child) is a healthy weight for their height and age.
Positive body talk
To help your tamaiti have a positive body image, do not compare their body to others. Talk about the amazing things their body can do – run, jump, skip, tickle – not what their body looks like. Role-model this in the way you talk about your own body and other people's. All bodies deserve respect. See the video in the recommended links below.
Finding out my child's BMI
If your tamaiti is at least 2 years old, you can work out their BMI using an online BMI calculator. You will need to know their weight in kilograms and their height in centimetres.
You need to use a calculator that is suitable for tamariki, as BMI is measured differently for adults. The calculator will tell you if your tamaiti is underweight, normal (a healthy weight), overweight (a slightly unhealthy weight) or obese (a very unhealthy weight) for their height and age.
To work out the BMI for adults, see Finding out if I am a healthy weight.
BMI result
BMI calculators for tamariki give the results as a percentile. This shows how your tamaiti compares to other tamariki of the same sex and age. For example, a girl on the 80th percentile has a BMI score higher than 80 out of 100 other girls her age.
Regardless of the BMI result, if you have concerns about their eating, activity levels, sleep, screen time or overall wellbeing, talk to your general practice team. They will be able to check for any underlying health conditions. They may also be able to refer your whānau (family) for healthy lifestyle support.
Underweight (on the 2nd percentile or below)
If your tamaiti is underweight, it might be because they have inherited this from you or their other parent. But it could mean they are not eating enough, or they have an underlying health issue. Make an appointment to see your general practice team. Find out more in Underweight children.
Healthy weight (between the 2nd and 91st percentiles)
Your tamaiti is likely to be a healthy weight for their height. Aim to instil healthy habits in your whānau so you and your tamariki can enjoy good health for life. See Healthy & active children.
Unhealthy weight (91st percentile or above)
If your tamaiti is an unhealthy weight, they are more likely to develop health problems. These could include high blood pressure, type 2 diabetes, breathing problems and joint pain. They are also more likely to become an overweight adult.
See Healthy & active children for tips on how to encourage your tamaiti to eat well and be more active. If you are concerned about their weight, talk to your general practice team. They may be referred to a healthy lifestyle programme.
If your tamaiti is an unhealthy weight and still growing, they do not need to lose weight. Staying the same weight while they grow taller will mean they will become a healthier weight for their height over time.
HealthInfo recommends the following videos
- Healthy Tasmania – Positive body image
The way you feel and talk about bodies and eating has a big impact on your tamariki. Teach tamariki to be confident in their own body.
Written by HealthInfo clinical advisers. Last reviewed March 2025.
SourcesReview key: HIHEC-62690
