Full disclosure-I work at Mayo in Communications. Frist want to thank (@kanaazpereira for moderating and @cynaburst for doing such a great job advocating for HCM patients and her blog HCM Beat.
I had a septal myectomy at Mayo (the team was amazing) about three years ago and am really glad I did it. As far as diet, I would say moderation; my case is unusual in that my appetite decreased after surgery and I have lost at least 40 pounds. I have followed up and the tests show that I'm healthy and my blood counts are good And don't be afraid to exercise after the surgery. A good thing about my cardio rehab was that the rehab team proved to me that I could work out with intervals training. I try to get my heart rate up to about 130 beats a minute several times during a half hour workout.