Justifications of illness...

Junk food (A) is normally considered unhealthy (B).

Being sick (C) is considered being unhealthy (B).

So if junk food is unhealthy, and being sick is unhealthy, then eating junk food equals a function of being sick! For the math-minded: if A = B and B = C then A = C

Therefore, because I am already unhealthy with a cold, it is just fine and dandy for me to devour chocolate and other such joys normally considered "unhealthy."