Are my big calves caused by fat or muscle? (Photo)

In the calves, a great percentage of the volume is usually muscle. Your photo does not allow a precise assessment.Calf reduction is possible but is somewhat complex.

   This cannot be determined well without examining you.Kenneth Hughes, MDLos Angeles, CA...............

Large
calves may be due to either bulky muscle, heavy underlying bone and/ or fat.
While it is difficult to assess the cause of your problem from the
photographs, a skilled board certified plastic surgeon should be able to
determine if the bulk of your problem is because of abnormal fatty deposits of
your legs. If this is the problem then new refinements in liposculpture
should be able to improve the shape of your calf. Typically this
procedure can be performed as an outpatient without the need for general
anesthesia.

There is no way to determine that without examining you. If there is excess fat, liposuction may offer modest improvement.