I prefer to call it the quantum effect but the community is sticking with mandela effect. I am going to refer you to a youtube channel for now, then if you want to discuss it or ask questions, I am pretty familiar with the changes most of us have logged. This is not a theory, or a conspiracy. Something has happened to shift reality or to shift those of us experiencing this. Check out this guy's channel and watch his voting videos.
https://www.youtube.com/user/MoneyBags73
I will embed one here. This is about Marilyn Monroe. She was skinny in this reality! She was a healthy woman in the one I grew up in.