More of a tip than an image.
I learned that a good way to make realistic anatomy is by projecting a image with the muscle tones on the body (preferably front and back).
Then sculpting out the muscles on the geomtry.
After which you can create a new sculpt layer and freely alter mass amounts of the sculpt. i.e. make it fatter, bigger etc with.
By having extra layers you can also vary the strength of the layer giving you variety between your base effect and your altared effect.