BMI (Body Mass Index) is a measurement of body fat based on height and weight that applies to both men and women between the ages of 18 and 65 years.BMI can be used to indicate if you are overweight, obese, underweight or normal. A healthy BMI score is between 20 and 25. A score below 20 indicates that you may be underweight; a value above 25 indicates that you may be overweight. BMI provided a simple numeric measure of a person's "fatness" or "thinness", allowing health professionals to discuss over- and under-weight problems more objectively with their patients. Body mass index (BMI) and waist circumference are two measurements to identify if you are at increased risk of developing health problems because of your weight.

Body mass index may not be accurate for those who are:

• Under 18 or not finished growing
• Naturally very lean or very muscular
• Of certain racial and ethnic groups
• Over the age of 65

You can calculate your BMI by  using the BMI Formula.

English 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 ) )

The BMI score means the following:

The second measurement is waist circumference. It may be easier to have someone else take your waist measurement. Place the tape measure half way between your hip bone and your lowest rib. This will be about 2 inches above your belly button. Ensure that the tape measure is level all the way around. Take a deep breath, breathe out and measure.

Men with a waist circumference of more than 40 in or 102 cm and women with a waist circumference of more than 35 in or 88 cm are at increased risk of developing health problems such as type 2 diabetes, heart disease and high blood pressure.

Put the two measurements together to determine your overall risk. Even for those with a healthy BMI an elevated waist circumference will indicate an increased risk. Other factors that put you at increased risk are:

• High blood pressure
• High cholesterol
• High triglycerides
• High blood sugar
• Not being physically active
• Cigarette smoking

The risks for each individual needs to take into account other factors such as lifestyle habits, fitness level and the presence of other health conditions. Talk to your doctor if you are at increased risk and need to lose weight. People who are overweight or obese have a greater chance of developing high blood pressure, high cholesterol, type 2 diabetes, stroke and certain types of cancer. Even a small weight loss, just 10% of your current weight will help to lower your risk of developing those diseases.