Will - when something like that happens, and although under HIPAA you don't owe anyone any explanations, I think that it would be the most politically correct thing to do to tell you co-workers:
- That you are acutely aware of the problem
- That it is a medical issue that you are struggling with (they clearly can see how thin you've become) but which should eventually resolve
- That you are doing everything you can to minimize the effects on others, but you regret that you aren't always going to be successful
- That you hope they will be understanding and that you are honestly doing the best you can