MANILA, Philippines  - Daybreak is happy hour in a world turned upside down at a trendy bar in the Philippines' financial district, the clientele young and loud and with a vague California accent.

Vodka cruisers and beer fly by the bucketful as good friends Cici, Pau and Jels go off duty along with the rest of the night shift in the nation's half-million strong business process outsourcing (BPO) workforce.

Even the hors d'oeuvres are edgy -- "drunken" shrimp and green mango soaked in pale pilsen -- reflecting the punishing lifestyles of the partygoers.

"I used to drink eight bottles of Red Horse at a time and still find my way home," said 28-year-old Cici, discussing a local brew known for its high alcohol content and often called "The Devil's Own Juice."

The group of young women really let their hair down on Saturdays, hitting bars, beaches or shopping malls all day so they can socialize with friends outside the industry and sleep at least for one night like a normal person.

Life in many ways is a blast for the young, single and educated in the outsourcing industry.

Entry-level jobs bring salaries of  $300  a month with the promise of triple that after a few years' experience -- good wages in a country where a third of the population live on a dollar a day.

Jobs are plentiful and can come with generous perks such as 13th and 14th-month pay, performance bonuses and free medical insurance.

And the outsourcing industry -- which has soaked up millions of call centre, accounting and other back-office jobs from the developed world -- is becoming an increasingly vital part of the nation's economy.

Its 500,000 Filipino employees are the world's second biggest outsourcing workforce behind India.

Its revenues, which already account for 5% of the country's gross domestic product, are growing at double digit rates annually, according to the industry group Business Processing Association Philippines.

On a more micro-level, entire 24/7 service industries -- including convenience stores, bars and fast-food restaurants -- have sprung up around the new office towers to serve the needs of the booming sector.

However there are concerns about the way the industry is reshaping young adult society, as well as the pressures the workers face as they remotely help customers and clients on the other side of the world.

The odd hours, irate clients, tedious workloads and performance demands often drive staff -- particularly call center workers -- to early burnout.

Cici, Pau and Jels -- who spoke to AFP on condition their surnames were not used -- are castaways from earlier call center jobs.

"Sometimes you would be handling 300 calls at once and 150 others would be on hold. You don't have a moment's rest," said Pau, 32, who graduated to a higher-paying job handling office equipment procurement for US companies.

She said call center staff typically got only two 15-minute cigarette breaks either side of a 30-minute meal break every eight-hour shift.

Cici said one of the hardest parts of call center work was simply dealing with customers angry at having to speak with someone on the other side of the world.

"One customer said: 'I don't wanna talk to you. I want to talk to an American'... I cried," Cici said.

And while Filipino BPO workers earn 53% more than same-age workers in other industries, one in three quit every year, according to an International Labour Organisation study released last month.

The turnover rate is four times the national average.

"Five years in one job is a long time in this industry," Cici said.

The arrival of the BPO industry a decade ago also brought about changes in values, diets, and sexual practices, according to Josefina Natividad, a professor with the University of the Philippines' Population Institute.

"What shocked us most was that for both call-centre and non call-centre workers the level of premarital sex was very high," she said, citing a health and lifestyle survey on young Filipinos completed by her team this year.

Heavy drinking and smoking, rising childbirths out of wedlock, and high consumption of junk food also stood out.

"The world is different now, and the single thing driving this I'm sure is technology," Natividad said.

Both Cici and Pau said they had heard similar stories in the call centre office they used to work at, which have beds in rest areas for exhausted staff.

"Our sleeping quarters were for both sexes. Some of my friends told me that there were certain things that happened there," Cici said.

The trend has worrying implications on public health, said Teresita Marie Bagasao, the country official for the United Nations Joint UN Programme on HIV/AIDS.

Most new HIV infections now occur among young Filipinos, compared with the 1990s when the country's large overseas-based work force including sailors were the main risk group, she said.

Despite the stresses and risks, those in the industry see few other options in a country where the only way they would earn that kind of money would be to join the exodus of Filipinos working abroad.

Jels said she had earned enough in 5 years in the industry to pay a deposit on a condominium unit, and said her priority now was to hopefully start a family.

"I want a boyfriend. And I want a family and a baby in 2 or  3years' time," the 29-year-old-said.