I have no idea. If you gain back the weight however, you should be fine. Sometimes, weight can fluctuate by 5 pounds in a week, somehow! I would watch it though. 
If you have any discomfort, fatigue, or other typical illness symptoms, make sure not to let your guard down. 
I remember once a day after flying, I got so ill that when I was eating something, I puked 5 pounds. IT WAS SO FUNNY (But it’s too abnormal)! 
I hope you will be well, though.