No expert here, but I think fasting can sometimes trigger disordered eating in some people. Binge eating, etc. People are just so varied and so is nutrition.
I haven't seen anything for healthy individuals. There are some studies though that have found negative effects for pregnant women and unborn children.
It also depends on what type of fasting you're talking about; Here's a video about "alternate day fasting" that shows it can mostly be good, unless you already have high cholesterol or are diabetic: https://www.youtube.com/watch?v=MKFWvYtm6Ck
(check out the recent videos on that channel as well - he's just done several videos covering scientific studies about all types of fasting!)
There are papers showing negative side effects (bulimia, eating disorders), but a point easily overlooked is that if you are not mentally prepared, it's a though ride.
Are there any that say fasting is bad?