I would say that in at least some cases over eating and anxiety are both symptoms of underlying problems. Stress, emotional issues, and trauma can all lead someone to either of the two.
As someone that uses food as a coping mechanism for stress, I agree with the GP - if the underlying problem isn't resolved, the weight will come back.
While one person saying this once is not necessarily harassment, the frame of reference has to be from the context of the recipient. Consider how often the author has to hear this or similar comments from customers as a result of being a woman working in a trade.
It sounds like from your perspective, being better looking than their co-workers is a good thing. By and large, men are going to find women better looking than other men. That means the "better looking" comment is directly pointing out that the recipient of the comment is a woman.
This article is talking specifically about the ways in which it is detrimental to be a tradeswoman. So in this context, being a woman makes it more difficult for this person to their job.
Looking at another example of something that would make being a tradesperson difficult: Would you call it harassment if customers were consistently making flippant remarks about a co-worker that was missing a hand?
As someone that uses food as a coping mechanism for stress, I agree with the GP - if the underlying problem isn't resolved, the weight will come back.