There may be additional cues in a picture as to health. But as far as fat stores; I look around the neck, at the limbs, the base of the tail, and around the hip joint area above the base of the tail...where any significant lack of fat will be evident by protruding bones.
Take particular note of the limbs of this cornutum female.
In the second picture, of my solare male, the definition is less visible...but I think it's a cool picture.

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"A man that should call everything by it's right name, would hardly pass the streets without being knocked down as a common enemy." The Complete Works of George Savile, First Marquess of Halifax 1912,246