With all that sweating your body lost a lot of salt and electrolytes. You need to replace it and your body is telling you so. But that doesn't mean you have to replace it with fries (althought fries would work for me ). Also, with heavy fast spinning your muscles are getting quite the workout too. The muscles will need protein to rebuild and repair after a workout like that. I usually carry a pria protein bar with me when I go to the gym for a workout. It stays off the cravings until I can get home and have dinner.

Sadly as much as I love soy milk it HATES me! I get terrible lower bowel pains and other things, ahem, 10 minutes after drinking anything soy.