Help, I'm sick!
How many pleas have we seen like this? You know what? If you're sick, focus on getting healthy first, then worry about what to eat and exercise. If you don't give yourself sufficient time to recover, you could just end up hurting yourself in the long run. You get sick because your body is no longer strong enough to fight off every invading "bug" that comes along. When you are fighting off the bug, don't worry about anything else. Your body will be working over-time as it is! The last thing you need when sick is to restrict your calories or try to exercise. If you try to, all you do is drag out the illness longer making it more difficult to get back on track when it's over. Yes, you may gain weight. A lot of it will only be water weight which you can flush out with lots of water. See why getting fluids is so important while you're sick? It truly can get you better faster.
When your normal workout is just too hard, or you're too tired to do much of anything, this is your body telling you that is needs some rest. Take it easier for a day or two. Be kind to yourself. Heal. If you can hear it saying please stop, listen! Your body really knows best. You have to listen to it. And when you're sick, it's never been as important! It will let you know when you can get back to your normal pace too. You'll crave it! It really does work!
It keeps boiling down to this... Listen to your body.