Vinnie Tortorich
Self - Narrator / Producer / Trainer / Author

Bret Scher
Self - Cardiologist

Gary Taubes
Self - Journalist / Author

Dave Feldman
Self - Software Engineer

Eric Westman
Self - Internal Medicine Doctor

Andreas Eenfeldt
Self - Physician

Drew Pinsky
Self - Physician

Georgia Ede
Self - Psychiatrist

Nina Teicholz
Self - Journalist

Vilhjalmur Stefansson
Self - Explorer (archive footage)

Ancel Keys
Self (archive footage)

Jeffry Gerber
Self - Physician

George McGovern
Self - Politician (archive footage)

Gary Fetke
Self - Orthopaedic Surgeon