A few years ago I went through about a two-month period of getting ill with various things -- tonsillitis, a stomach virus, and the mono. So I couldn't eat because my throat was swollen, then I couldn't eat because my stomach wasn't accepting much of anything, and then I couldn't eat because I was too tired.

After I finally got healthy -- well, "weak as a kitten" was far stronger then I was. All I could do was sit on a spin bike at the gym for 40 minutes, all resistance off, and spin away, which is about 30 watts for 45 minutes. But the good news -- my fitness level really did come back fairly quickly. Six weeks after I was medically cleared to ride again I did a 75 mile ride through the Berkshires (i.e., not exactly flat).

So don't despair too much -- once you get back on the bike, you'll return to form mighty fast.