Does she seem stressed at all? I lost a load of weight when I was stressed about my M. I sort of woke up and realised I didn't know the guy next to me in bed anymore or what I wanted out of life. The kids were at school and no longer seemed to need me so much etc etc.
Often there is an OP involved but there doesn't always seem to be.
Unlike the guys on here I do wonder if this is something that has been brewing in your W's mind for a while and the weight loss is due to the stress of being so unhappy and her trying to work out what she is going to do. How long is it since she really talked to you about hopes for the future etc etc? that's when I sort of new things were wrong.....when neither of us seemed to care any more and talk about things....we existed....the P'ship had gone. I found I told my GF's the sort of things I should have been discussing with my H....just because I felt when I talked to him it was such hard work and would most likely end in a row. We just sort of learned to lead separate lives.
We did manage to sort it so don't give up hope.
As for the buying new clothes....well I went from a 14/16 down to a 8/10....you do need to buy new clothes- including underwear....I went to Tesco's one day and realised my jeans were like those ones you see one teenage boys when they are showing off half their boxers.......I was a bit ashamed- luckily I had a long fleece on
Saffie me 46 H 46 M in 1986 D20,D18,S16,D13 H's A 01/05 to 07/06 H recommitted to M 07/06 renewed vows 09/06 Going from strength to strength