Bone structure varies in size from person to person. In order to determine your optimal weight, researchers added frame size as a factor. The sizes are categorized into three categories: small frame, medium frame and large frame. There are two methods of determining frame size:

The Elbow Breadth Method
You can also calculate your frame size by measuring the breadth of your elbow.This is a little more complex but provides a accurate results.

How to measure Elbow Breadth
1.Extend your arm forward so that it is horizontal and parallel to the ground.
2.Turn your hand so your palm is uppermost. Bend your elbow so your forearm is at 90º to the ground.
3.Use your forefinger and thumb as a gauge to determine your elbow breadth by measuring the gap between them with a tape measure or ruler as indicated on picture on the left.