That happened to me after trying the South Beach Diet. I would workout pretty intensly for an hour or more and try to eat dinner and it would not stay down. This happened for 4 days in a row. I emailed my Training Peaks.com and they told me it sounds like my blood sugar is too low and its making me sick, I needed more carbs. Sure enough I put carbs back in and I was fine. It's crucial to fuel your body before a intense workout. About a 1 1/2 before a workout is a good time. I find Cheerios,Oatmeal or Pb & J work best for the mornings. Also carry GU or something with you if you know it's going to be a extra intense ride.

Take Care,
Kim