Weight

 Taken from a post by K9 Solutions Dog Training (thanks!) called Killing them with Kindness

..This chart which might make it more helpful for people to understand how a little bit of weight can be more of a problem than they realize.

In toy breeds 1 pound of extra weight = 31 pounds on a human body
+2 lbs = 63
+3lbs = 94

In small breeds 2 lbs of extra weight = 13 lbs on a human body
+4 lbs = 26 lbs
+6 lbs = 40 lbs

In medium breeds 4 lbs of extra weight = 17 lbs on a human body
+6 lbs = 25 lbs
+ 8 lbs = 33 lbs

In large breeds 6 lbs of extra weight = 11 lbs on a human body
+8 = 14
+10 = 18 lbs

In giant breeds we are equal 10lbs = 10 lbs and so on.
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Here is a chart that lets you see how to assess your dogs body condition:

http://www.placervillevet.com/canine%20body%20condition.htm