Why Do We Calculate BMI for Children?
BMI for children is an important indicator of overall health, especially in the face of increased child obesity. Child BMI data collation is mandatory in the UK, but not everywhere. Nevertheless, globally schools are seeing that they can improve child health and well-being outcomes by screening for BMI.
How Evaluating BMI for Children Differs from that for Adults
In general, your body mass index (BMI) is a measure that uses your height and weight to work out if your weight is healthy. The BMI calculation divides your weight in kilograms by the square of your height in metres.
For adults, this works fine as it is, because the BMI of adults remains constant, regardless of age, unless you gain or lose a lot of weight. However, assessing the BMI for children is more complicated because a child’s BMI changes as they mature. Growth patterns differ between boys and girls, too. So, the age and gender of the child need to be considered when looking at BMI.
Age and gender variations are considered by comparing the child’s dimensions with a reference population. In England, this is a large sample of children taken in 1990 (UK90). Other countries have their own reference populations and there is some used for international comparisons and by global organisations, such as the WHO. For more information, see this guide to classifying BMI for children.
What’s Wrong with BMI for Children (or anyone else for that matter)?
Some criticise BMI for not giving an accurate picture of underlying health. There are many critiques, including one by UCLA in 2016, which found many people with overweight and obese BMI scores were perfectly healthy. And also, that 30% of those with “healthy” BMIs were in fact not healthy at all, based on their other health data.
Much of the criticism of BMI revolves around the fact that muscle weighs more than fat, and BMI can’t distinguish between them. So, some very fit, lean, muscular people have higher BMI scores than some with low-muscle/high-fat bodies.
Also, the location of fat is important; visceral fat around organs being much more dangerous to health than the same amount of fat spread evenly over the body.
Lastly, ethnic origin can be an important factor, missed by BMI. Some Asian people with BMI scores of under 25 can still have significant health risks.
Note that many of these criticisms relate to adult data, not BMI for children.
Child BMI’s Not Perfect, But it’s a Good Indicator
Nevertheless, BMI is a good indicator of health for broad population data. It’s relatively easy to measure and can inform public health policy, supporting childhood obesity prevention programmes, for example.
The UK’s National Child Measurement Programme (NCMP) was set up in line with the government’s strategy to tackle obesity, and to:
- inform local planning and delivery of services for children;
- gather population-level data to allow analysis of trends in growth patterns and obesity;
- increase public and professional understanding of weight issues in children; and
- be a vehicle for engaging with children and families about healthy lifestyles and weight issues.
The American Heart Association use BMI as an indicator of heart health, too. They have found that:
‘Maintaining a healthy weight during childhood is especially important for heart health. Research shows that nearly 60 percent of overweight children aged 5 to 17 had at least one risk factor for cardiovascular disease. 25 percent had two or more’
Data Collection and Administration are Vital
If you operate in an environment where you require specific data, be sure to follow the service specification provided. A good example is the UK’s NCMP. SchoolScreener® helps by making the administrative side of child BMI screening easier for you, consistent and compliant with the NCMP guidelines.
The same applies if you’re working without the strict national guidelines of the UK model. In the USA, for example, while childhood obesity is a recognised challenge for public health, there is no consensus of how screening should be undertaken. SchoolScreener® helps by making the process of screening for child BMI easier and reducing the administrative burden of collecting data and reporting results to parents.
BMI for children is by no means a perfect indicator for health on an individual basis. That said, it certainly is a good indicator when viewed on a broader scale. SchoolScreener® makes the administrative process simpler and, where there are strong government guidelines in place, ensures compliance.