Deputy Prime Minister Nick Clegg is set to pledge an extra £150m of funding to help children with eating disorders.
The aim is to invest in preventative therapy to cut the need for hospital treatment.
The money, earmarked in this year's Autumn Statement, comes after figures show that admissions for eating disorders among young people have been rising in England.
Experts have been warning that current services are not always up to scratch.
In many parts of the country, cuts and frozen budgets along with increasing demand have left child and adolescent mental health services struggling to cope, the Health Select Committee said last month.
And cases of teenagers being treated on adult wards, held temporarily in police cells or sent hundreds of miles from home for care have made the headlines recently.
Mr Clegg will say he wants to see services transformed, with the focus shifted from expensive institutional care to targeted community-based provision.
Eating disorders cost the NHS around £200m a year, and the bill for in-patient care averages out at £98,750 per admission.
From 2012 to 2013, there were 2,560 hospital admissions for eating disorders in England - a rise of 8% on the previous year.
One in five of those taken into hospital with an eating disorder was admitted and discharged on the same day.
But one in 17 stayed in hospital for longer than six months.
Sarah Brennan, chief executive of Young Minds, said: "It is great news indeed to hear that areas of support for children and young people's mental health will receive additional, desperately needed, resources.
"Too often children and young people's services are overlooked in preference for adult services. Young people make up 20% of the population, yet receive a fraction of the resources available with the terrible consequences we hear about daily in the news.
"We trust this is the beginning of a new approach by government and commissioners nationally."