The Body Mass Index (hereby referred to as the BMI) is a common measurement when it comes to weight.  What exactly is the BMI and how useful is it when it comes to weight? Read on to learn more.

What is the BMI?

The BMI is a number that is calculated using a person’s weight and height.  It is an indicator of the amount of body fat that people have and can help you tell if you are a healthy weight for your height.  The formula is a person’s weight in kilograms divided by a person’s height in metres squared.  For example it could be 68kg/ (1.65m) 2 which equals 24.98.
The BMI is intended to be a tool to identify possible weight problems for adults; however it is not a diagnostic tool.  That is, a person may have a high BMI but other tests are needed to determine if excess weight is a health risk.
But what does the BMI mean?  Here are the following weight categories that have been assigned to varying BMIs:
• Below 18.5 – underweight
• 18.5 – 24.9 – normal
• 25.0 – 29.9 – overweight
• 30.0 and over – obese
• 40.0 and over – severely obese

How reliable is the BMI?

Generally speaking, the BMI is a fairly reliable indicator of the amount of body fat that a person has. However, there are some situations in which the BMI may not give an accurate reading.  At the same BMI, women tend to have more body fat than men.  Also, at the same BMI, older people may have more body fat than younger adults.  Athletes and people that get lots of exercise may also have a higher BMI as they have more muscle rather than more body fat.  Pregnant and breastfeeding women may also have incorrect BMI readings.

The BMI is calculated in the same way for children as it is for adults but the criteria used to interpret the results are different from those used for adults.  For children and teenagers, age and sex specific percentiles are used as the amount of body fat changes with age and the amount of body fat also differs between boys and girls.

What if My BMI Is Too High Or Too Low?

If your BMI is over 25 then you should consider losing weight as excess weight is a risk factor for many health conditions including heart disease, diabetes, osteoarthritis, high blood pressure, gallbladder disease and several forms of cancer such as colon and breast cancer.

If your BMI is less than 18.5, you may be at risk of conditions such as compromised immune function, respiratory disease, digestive disease, cancer, osteoporosis, and an increased risk of falls and fractures.