Dietz attended Case Western Reserve University and received his bachelor's degree in 1919.
In 1921 he took a position as science editor for the Scripps-Howard Newspapers, a job he kept until his retirement in 1977.
Dietz was a member of the Publicity Committee of the United States National Research Council's Division of Medical Science and of Harvard University's Institute on War Problems, and was a consultant to the U. S. Army Surgeon General from 1944 to 1947.
Dietz was recognized many times during his career for his contributions to science journalism.
For "coverage of science at the tercentenary of Harvard University" in 1936, with Scripps-Howard, he shared the Pulitzer Prize for Reporting with writers for four other publishers.