According to the NHLBI guidelines, assessment of overweight involves using three key measures:

body mass index (BMI)

waist circumference, and

risk factors for diseases and conditions associated with obesity.
The BMI is a measure of your weight relative to your height and waist circumference measures abdominal fat. Combining these with information about your additional risk factors yields your risk for developing obesity-associated diseases.

What is Your Risk?
1. Body Mass Index (BMI)
BMI is a reliable indicator of total body fat, which is related to the risk of disease and death. The score is valid for both men and women but it does have some limits. The limits are:

It may overestimate body fat in athletes and others who have a muscular build.
It may underestimate body fat in older persons and others who have lost muscle mass.
Use the BMI calculator or tables to estimate your total body fat. The BMI score means the following:

BMI
Underweight Below 18.5
Normal 18.5 - 24.9
Overweight 25.0 - 29.9
Obesity 30.0 and Above