His plea before U.S. District Chief Judge William T. Moore Jr. abruptly ended three days of trial in the case.
As part of the negotiated plea, Dr. Lentz, 41, admitted his role in the conspiracy count.
Assistant U.S. Attorney Brian McEvoy said Dr. Lentz also agreed to pay restitution of all Medicare payments he received under his provider number.
In return, prosecutors have agreed to dismiss more than 100 other counts of health care fraud against Dr. Lentz and recommend that he receive credit for acceptance of responsibility toward his sentence.
Mr. McEvoy also told Judge Moore prosecutors will dismiss all charges against co-defendant and wife Rebecca Jill Lentz in return for her participation in a pre-trial diversion program.
Judge Moore will impose sentence later after completion of a pre-sentencing investigation by probation officers.
No sentencing date was set.
Dr. Lentz and his wife were on trial for scheming to defraud Medicare and Georgia Medicaid of more than $600,000 in payments for services at Lentz Medical Practice and World Gym in Jesup.
Both initially pleaded not guilty to the charges.