Depends what you're doing and who you're doing it with. BMI usually lower than 27 required (big issue) and cholesteral normal. For the rest, if you dip the phsycho or interview, they'll probably tell you that you failed the medical. As far as the NASA theory goes: Deke Slayton (amongst other things) flew the Apollo Soyuz link up in the summer of 1975. He had dicky heart and passed that one.
