"He (Jagan) is continuing with his fast and did not take lunch and dinner even today," Chanchalguda Jail Superintendent B Saidaiah told PTI adding his health condition was stable.
Jagan began his indefinite hunger strike on Sunday.
YSR Congress honorary president Y S Vijayamma had called off her indefinite fast on August 24 opposing proposed bifurcation of Andhra Pradesh after she was forcibly shifted to a hospital in Guntur.
She had then announced that her son and jailed Kadapa MP Jaganmohan Reddy would undertake an indefinite fast seeking "justice for Seemandhra people.