Not eating when sick?

I'm sick and I haven't eaten today. I have had a bottle of vitamin water zero but thats it. I am a runner, cyclist, and a martial artist, but I haven't worked out today or yesterday. I am afraid I will gain weight since I am not exercising. I have a sore throat, I'm congested, and I have a little fever, I also have a headache. Is it ok if I dont eat, or will it make me more sick?