I believe this is By Light Alone (2011) by Adam Roberts.
Synopsis from Goodreads:
In a world where we have been genetically engineered so that we can photosynthesise sunlight with our hair hunger is a thing of the past, food an indulgence. The poor grow their hair, the rich affect baldness and flaunt their wealth by still eating. But other hungers remain...
The young daughter of an affluent New York family is kidnapped. The ransom demands are refused. Years later a young women arrives at the family home claiming to be their long lost daughter. She has changed so much, she has lived on light, can anyone be sure that she has come home? Adam Roberts' new novel is yet another amazing melding of startling ideas and beautiful prose. Set in a New York of the future it nevertheless has echoes of a Fitzgeraldesque affluence and art-deco style. It charts his further progress as one of the most important writers of his generation.
And this review from The Guardian mentions that the story begins at a ski resort on Mount Ararat:
It's about a hundred years in the future. The poor are living on sunlight, which they absorb through their hair. A woman can't sustain pregnancy on this miserable diet, so there's a big shift: the masses are chronically short of children; and that's going to be important. The story itself begins at a ski resort on Mount Ararat. Three couples, holiday acquaintances, parade their callous affluence. They are proudly bald and mountainously fat; they have disgusting table manners and engage in joyless, thunder-thighed illicit sex. They are nasty to the local staff, and ignore their own small children, whose "carers" must produce these trophy objects for a few minutes' display, before quickly removing them again. Then Leah, the older child of the central couple, George and Marie, disappears. The regional police take a relaxed view; they explain that child kidnap is commonplace, then arrest the "carer". The motive is not ransom, the girl will not be returned: and that's the end of that.