Well, as eductaed as many guys may be about all of this, and as risk-free as some may think it is, there is little argument with the fact that there are always SOME risks to this lifestyle.
Maybe to her, having you lead a low-risk life, and being as healthy as possible, is what is the most important.
And before 20 kids jump on my ass and go "uh ... there is no risk, etc etc etc" get real. There are SOME risks, and education and all may lower them to a GREAT degree, but there ARE risks.
Plus, I know many guys may not agree with this (and I don't care, LOL) but most women if they are really in love with you, dont care much about an extra 20 lbs of muscle. Your health and well-being are far far more imprtant to them.
Marriage, ones that WORK, are abotu in part, the ability to compromise. Hopefully decisions such as this come about becuase BOTH of you have discussed things and have dtermioend what is the best trade-off for both of you.
Be well.