Body Conditioning System

Each time your dog or cat visits for their annual wellness exam, the doctor performs a thorough examination of your pet.  One of the the tests they measure is the Body Condition System.  This tells you as an owner whether you pet is underweight, overweight or ideal.  The scale is based on a 1-9 range with a 5 being the ideal weight range. 

Sources:
http://www.purinaveterinarydiets.com/resources/Files/dog_chart.pdf