Depends

• anti aging for the skin(looks ) : plastic surgery /dermatology

• anti aging as in extending life after certain serious conditions: chronic diseases specialist or oncology

• anti aging as a field in itself to literally stop aging or rather make sure ur body is at the same age (as in replication of the exact amount of cells u lose per second (not even one more or less) . Having extended telomeres at the end of the genomes . : genetics .

• u should really look into genetics and crispr and epigenitics and eugenitics