I think what it meant was that people are 100% unable to change their weight only in the sense of weight loss, and any deliberate attempt to change their 'natural setpoint weight' will cause excruciating pain or hunger of some sort(in the process of 'unnaturally losing the weight') which qualifies as an 'eating disorder'. I found it really insulting to those with real eating disorders and it trivialises and glamorises the issue to simply 'muh diet culture'.