1: https://well.blogs.nytimes.com/2013/07/24/can-you-get-too-mu...
2: https://en.wikipedia.org/wiki/Graeme_Obree#Taking_the_record
If you work out in the cardio section of any gym, you will eventually see regulars who are hitting some machines very hard, with a visual appearance of anorexia. I'm sure some of those people were just skinny, but not all of them. It's not my role, as a fellow gym member, to recommend psychiatric help. But heavens knows I thought it, more than once.
In addition, gyms are built around luring in people while assuming that a large percentage of them will quickly stop attending. Some of the drop-off is just from laziness or dislike of exercise. But some of the drop-off is from going too hard, too fast, resulting in injury, especially for first-time weightlifters.