I had a horrible time but going the other way, gaining weight. When I was in nursing school we all went off to our ward rotations for 9 months where we didn't see most of the other students, and then we were back in class for a final four weeks. The ward rotation with awful shifts, sleep deprivation, stress, severe stomach bug contracted just prior to the ward rotation, added to pcos, insulin resistance and severe reactive hypoglycemia, meant in 9 months I put on a huge amount of weight - not sure exactly how much but around 140 lbs (no I hadn't been stuffing my face, and I had been really active).

To say the other students were shocked when we returned to classes is an understatement, and I got constant stares, comments, and yes, people pulling me aside and telling me how worried they were about my health. Also the 'do you realise you've put on weight' (of course not, I just thought my clothes had shrunk and all reflective surfaces had turned into fun house mirrors /sarcasm).

People are really weird about weight loss and gain, and often speak to the person like somehow they might be unaware that they had lost or gained weight. If someone looks like a skeleton and never eats in front of anyone, or has other signs of a possibly life threatening eating disorder, then by all means an intervention may be appropriate, but otherwise it helps no one to point out the blindingly obvious.

Also I wonder if, with weight loss, the person saying 'I'm concerned for your health' or 'you've lost enough now', is actually them meaning 'I'm uncomfortable with the changes you're making, it makes me feel worse about myself'.