Body Mass Index

The body mass index is a ratio figure to indicate your weight compared to your height. It gives a good indication in most people as to their physical body fat to lean tissue composition. It does have its limitations and I am no longer convinced that it is that accurate for myself as I haven't gained any "size" yet my weight has gone up since getting very physically active suggesting I have become much more muscular. I prefer using the body fat percentage method to look at my physical composition as that gives me a figure which I think reflects my physical body better. I'll post that later.

Calculating your BMI is easy - there are a number of online calculators of which I have posted links at the end of this post. 

However if you want to do it for yourself then you can use the calculations below.

You will need your bathroom scales, tape measure and a pen and paper to do this plus a calculator if you are mathematically challenged! If possible get someone to assist you as measuring your height if it's unknown can be a bit tricky.

Using the scales, measure your weight in either pounds or kilograms. There are 2.2 lbs approximately to a kilogram and there are 14 lbs to a stone of weight. If you measure your weight in lbs, measure or use your metric height converted to inches. There are 12 inches to a foot and there are 2.54 cm to an inch.

Imperial BMI Formula

BMI = ( Weight in Pounds / ( Height in inches x Height in inches ) ) x 703

Metric BMI Formula

BMI = ( Weight in Kilograms / ( Height in Meters x Height in Meters ) )

A BMI of less than 18.5 is considered Underweight. This is unhealthy. 

A BMI of between 18.5 and 24.9 is considered normal/healthy.

A BMI of between 25 and 30 is considered overweight which starts to increase your chances of illness and poor cardiovascular and respiratory health.

A BMI of 30 or more is considered obese and this will greatly increase the risk of you developing cardiovascular and other health problems. Risk of heart attacks and strokes and other medical conditions such as sleep apnea are of significant increase.

As a final thought to this remember, if you train lots, especially for hypertrophy (enlarged muscles-bodybuilding) you are likely to have a high BMI. If this sounds like you, I suggest you do a body fat analysis instead to look at your lean to fatty tissue ratio. In older people it can give a false "reading" too as they tend to have a lot of muscle wastage.

Next Blog...calculating BMR and daily caloric needs.

Links to online calculators:

http://www.nhs.uk/Tools/Pages/Healthyweightcalculator.aspx - very good and approved by the British National Health Service
http://www.nhlbisupport.com/bmi/