In order to have a healthy weight, one must have the right Body Mass Index, also known as BMI. It is the measurement of the body fat based on the height and weight of adults falling between the age group of 18 to 65. It is a reliable method to know how much and if at all you need to lose weight. This method of measuring body fat is often used by doctors as well. Body mass index is calculated by dividing an individual's body weight by the square of his or her height.

BMI categories
* Individuals of BMI of 18.5 or less fall under the category of underweight and need to gain weight.
* Between 18.5 to 24.9 is considered to be a normal BMI, people in this category are healthy.
* Between 25 to 30 is overweight and individuals falling in this range need to watch their weight.
* Over 30 is obese and people in this category need to take serious measures to lose weight.

You can know what your BMI is from the following chart and see if you need to lose weight.

Image source: US Dept of home and human services website

Yes but BMI can be very inaccurate for extremely muscular people. It will tell you that you are extremely overweight but you aren't...

Good point Jongin .. That proves BMI is an approximate calculation only.