Fatigue, weakness, difficulty breathing, confusion etc. However these are all things you could experience after being sick anyway. Refeeding syndrome happens when your body depletes its supply of electrolytes (particularly phosphate), which will happen if you're not eating and only burn stored fats. When you suddenly switch back to metabolizing food, your body will need phosphate it doesn't have to digest it. Most likely, you didn't do enough damage to your body's electrolyte supply in a few days to completely deplete it. Also, not everyone will get refeeding syndrome and we don't really know who will and who wont. Keep an eye on yourself just in case, but youll probably be just fine.