I've been fasting on Saturday and half of Sunday. My allergy symptoms have subsided and overall I seem to be healthier. Technically I don't do an actual fast because I allow myself low calorie and low sugar liquids like almond milk as long as I stay below 200 calorie limit.
As always consult with a doctor before changing your diet regimen but my anecdotal evidence is on the positive side.
I think most people tend to overeat and most people also have some low grade food allergies so they have constant internal inflammation. In my case the health benefits seem to come from reduced inflammation because my sinus allergies subside and that's how I know I'm generally feeling better.
I haven't yet figured out what it is exactly I have a low grade allergy for. I know dairy products tend to make things worse but I already knew I was lactose intolerant so that one is expected. Gluten and grains I seem to be ok with so I don't think I have the latest hipster allergy.
Forgot to mention another benefit of fasting is that thinking is easier. I don't know why but in general on the days that I fast I feel less sluggish.