I'm sure there has. For me, the research I pay the most attention to is my own. 

There's a ton of research on the health benefits of long-term fasting. I do have to say I felt great afterward.

mudbloodvonfrei

It helps a ton. It's amazing how much energy we can get from salt. I had a similar experience when I started fasting. Now I tend to drink some salt water. What was the intentions with your fasts? 

DesertDave

alter_native

What's the longest you have gone without food, and why?

Four day fast. Only water with some salts added to replenish electrolytes. I did two three-day fasts a long time ago and it a rough time starting day two. The electrolytes made all the difference.