@FizzyPink
I’d love this but then I’ve lost 10lbs recently and no one seems to have noticed.
On the flip side I hate “oh don’t you look well”
I hate 'you look well' too.
It's secret code for 'you've gained weight.'
I know a young woman who had suffered an eating disorder for much of her life (since around 13-14 years old.) She was 13 and a half stone at the age of 20, and at that point she decided to do something about it, and started eating healthier, and exercising more.
She dropped from 13 and a half stone to 9 and a half stone in around 9 months. Loads of people said she looked great for losing the weight/much healthier/looked nicer in clothes etc...
But she got a couple of apparently well-meaning people (one older relative, and a neighbour of her parents,) saying she had lost too much weight, and looked 'too thin.' 9 and a half stone at 5 ft 4 is not too thin, but hey...
So anyway, she regained half a stone over Christmas, and ONE of the 'well-meaning' people (her older relative,) said 'ooh, you look so much better now you've gained some weight...' 
Result; she lost another 2 stone, dropped to eight stone, and her eating disorder became much, much worse.
So IMO, it's OK to tell someone they have lost weight and they look good with it, but saying they have gained it is unacceptable. It's much worse. The VAST majority of people want to be slim/athletic, but NO-ONE wants to be fat. There are so many negative connotations to it, that you'd have to have rocks in your head to prefer being fat.
So it's pretty obvious that people much prefer being told they have lost weight. And most people will say they look better, because 95% of the time, they do (if it's a healthy lower weight!) As I said earlier, most people look better not fat!