BMI Calculator

We thought long and hard about including Body Mass Index on No Spoons to Cook.We decided we would include it because the BMI is a tool that is used to beat us over the heads with any time weight is raised by the medical profession.

Rather than ignoring it, like we’re sure most of us want to, we thought talking its use and limitations of the tool might help some better inform conversations with your clinical care teams.

What is the Body Mass Index

The Body Mass Index (BMI) is a widely used measure for assessing body weight relative to height. Most of us would have covered the BMI at school in health sciences or sports classes. Spoonies would no doubt be far more familiar with its use in a healthcare context.

It uses height and weight to calculate a range that provides an indication of overall health and risk factors for chronic diseases.

BMI is a tool to guide conversations; it is not a gospel of what is optimal health.

The Body Mass Index (BMI)

Understanding the limitations of the BMI as a tool

The over simplification of the tool is probably it’s biggest weakness. Explaining the relationship between height and weight is a simple conversation (even though there’s more to healthy bodies than weight and height alone). Understanding the limitationsmay help you with conversations with your care teams.

BMI doesn’t account for body composition.

It doesn’t distinguish between muscle, fat or bone mass. People with high muscle mass (like athletes) are often classed as being obese despite being fit and healthy. It also means that people with low muscle mass but high body fat may have a normal BMI, masking potential health risks.

BMI is calculated on norms for certain populations.

It doesn’t take ethnicity into consideration, it’s based on norms for Anglo-Saxon body composition. Population groups that are typically smaller or larger will typically be incorrectly classified on the BMI. It should not beused for children and adolescents; their bodies are still growing.

BMI doesn’t consider distribution of fat.

It cannot determinewhere fat is located in the body. Belly fat and visceral fat (fat around organs) is associated with higher health risks than fat in other areas of the body. People with the same BMI may have different health risks based on their fat distribution.

BMI doesn’t assess overall health.

BMI is a measure of weight relative to height only. It does not take into account other factors that affect health. Critical factors like diet, exercise, age, specific medical conditions and impacts of medications are not part of BMI calculations.

Risk of wrong weight classification.

BMI categories (underweight, normal weight, overweight, obese) are based on arbitrary cutoff points, and people near these cutoffs may be misclassified. BMI may not accurately reflect health risks for individuals at extreme ends of the weight spectrum, like people with a lot of muscle or have high bone density.

Calculate your BMI

Basic Information
Your results:
Basal Metabolic Rate (BMR):
Body Mass Index (BMI):
Target calorie intake per day:

Reference Ranges

Body Mass Index Ranges

Remember, the BMI is a tool to guide conversations, it is not a gospel of what is optimal health.

Weight ClassificationBMI RangeRisk Indicator
Normal18.5 - 24.9Average
Overweight (Pre-obese)20.0 - 29.9Increased
Obesity (Level 1)30.0 - 34.9Moderate
Obesity (Level 2)35.0 - 34.9Severe
Obesity (Level 3)<40.0Very Severe

Basal Metabolic Rate

Basal Metabolic Rate (BMR) is the amount of energy you use at rest. Basically, if you are doing nothing, this is what your body will use to simply exist.

Estimated Total Calorie Intake

I think looking at calories alone is a bit daft. It doesn’t take the nutritional benefits of what we’re eating into account. It simply says this is the amount of food we need to eat to keep our bodies running properly.

A more helpful way to look at what we should be eating is using a Macro Calculator. Macros break the calories into groups of the types of foods we should be focusing on to meet our daily energy requirements.

These are generic tools and provide a general guide based on normative ranges. Australian clinical practice uses the Harris-Benedict Equation and BMI. The tools on their own do not consider your current health status, medications and other things they may impact your dietary needs. For individual advice, consider speaking to your general practitioner, a registered dietician or your preferred healthcare professional.

Looking for something more useful?

Calculate personalised macros based on keto, low carb or Australian Dietary Standards.

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