I think that there are lots of people, both very slim/skinny and overweight, who have disordered relationships with food, or who use food to deal with emotions, or to exercise personal control when in situations that they feel are not within their control. That can apply to under and over eating.
Food is used to control us as children, from things like feeding routines, particular foods deemed 'treats', being made to 'clear your plate', sadly for some food being withdrawn as a punishment, offering a biscuit to sooth a child with a grazed knee, all these things set patterns that can and do carry over into adult life.
The above, along with societal issues about how 'we' [particularly women] are meant to look, It is no wonder so many people have unhealthy attitudes about eating.
There are so many emotional issues, tied up with eating and body image. I have known of girls/women, who have over eaten in a subconcious attempt to 'hide' or make themselves invisible, or unattractive, in those cases it was related to sexual abuse/assault, nothing to do with being lazy, but self preservation/protection.
Understanding rather than scorn is needed IMO.
We should all be kinder to each other.