Atlanta ? Dr. Thomas Frieden has swung a big stick as New York City’s top health official, pushing through bans on smoking and artery-clogging trans fats.

The New York Post called him “Dr. Buttinsky.” Others attacked him as a wrong-headed crusader. But smoking plummeted and the city made admired inroads against cancer and other chronic diseases.

On Sunday, he heads to Atlanta. And on Monday he takes over the federal government’s top public health agency, the Centers for Disease Control and Prevention — where he’s going to have to try a different approach.

At the CDC, the 48-year-old physician will command a larger agency, but one with few regulatory powers and more political headaches. Any campaigns against smoking, obesity and other health dangers will have to be won more with carrots than sticks, public health experts say.

“He can’t walk across the hall and find a sympathetic mayor and get stuff through. It’s a different playing field,” said Dr. Jeff Koplan, a former CDC director who fell out of favor with the Bush administration.

A key to succeeding in the CDC job will be whether Frieden can influence other federal agencies, state and local health departments, and health authorities around the world, experts said.

In an interview this week with The Associated Press, Frieden acknowledged the challenge and said partnering with other agencies will be more crucial than it was in New York.

“It’s really very different,” he said of his new job.

He listed smoking as the nation’s No. 1 health issue, and stressed the importance of fighting preventable illnesses. But in carefully worded responses, he did not reveal plans for any new campaigns, saying his initial goal is to work with CDC staff to build future plans.

Was being head of CDC something he aspired to? “I’ve never really thought about the next job,” he said.

Until this week, Frieden ran the New York City Department of Health and Mental Hygiene, one of the nation’s largest local health agencies, with an annual budget of $1.7 billion and a staff of more than 6,000.

The CDC and its sister unit, the Agency for Toxic Substances and Disease Registry, have a combined budget of about $10.1 billion and more than 14,000 full-time, part-time and contract employees.

The CDC is well-regarded but has had its problems.

The agency investigates disease outbreaks, researches health problems, and promotes illness prevention. CDC officials lead the federal response to threats like swine flu, SARS and food poisoning outbreaks. In a 2007 Harris Poll, the CDC was rated as the government agency that does the best job.

But internally, the agency was demoralized. Employees complained about a reorganization that added new layers of bureaucracy, and knocked CDC brass for sometimes going along with Bush administration political positions at the sacrifice of science.

Frieden arrives with a data-first reputation, earned partly through his decision at the start of his New York tenure in 2002, to survey the city to identify the most pressing health issues.

He used the information powerfully, to set goals, clear away opposition and energize his staff. “He impresses upon people the importance of their work and the ideal of improving the public’s health. He gets people whipped up,” said David Vlahov, a member of the New York Board of Health.

Colleagues describe him as smart, direct, a careful listener, a skilled communicator, a bit reserved with most people. Oh, and very determined.

“He scares some people,” Vlahov said.

Frieden was a CDC disease investigator in 1990 when he was assigned to New York City and worked on a large outbreak of drug-resistant tuberculosis. He stayed there, taking a job heading the city’s tuberculosis control. Cases of multidrug-resistant TB dropped by 80 percent.

In 1996, he began working in India with the World Health Organization on tuberculosis control. “I hadn’t planned on coming back. I sold my apartment in New York,” he said.

But New York Mayor Michael Bloomberg, elected in 2001, tapped him to be the city’s health commissioner. Bloomberg is known as a political and philanthropic champion for public health and he firmly backed Frieden and his plans to attack chronic diseases.

In 2003, the city banned smoking in almost all workplaces, a precedent-setting move that inspired other cities to do the same. New York also instituted cigarette tax hikes. Health officials estimate the city has 300,000 fewer smokers now than in 2002, which should translate to fewer cancer cases.