When it comes to quitting smoking, cold turkey beats slow turkey, according to a new study from the University of Oxford.

Oxford researchers divided almost 700 smokers into two groups. One group was asked to quit suddenly, while the other was asked to do it over time.

Smokers in both groups picked a date on which to smoke their last cigarette. But while the abrupt quitters kept up their usual nicotine habits until that date, the gradual quitters worked out a timetable for phasing out their smoking.

The results were clear: Four weeks later, 49 percent of the sudden quitters had quit smoking, while only 39 percent of the gradual quitters had managed to do so.

The study’s lead researcher, Dr. Nicola Lindson-Hawley, said coming up with a phase-out schedule may have done the slow quitters more harm than good.

“It provided them with an extra thing to do, which may have put them off quitting all together,” she said.