The real key is what you eat: cut out sugars and refined flours and instead eat as many vegetables as possible, say researchers from Stanford University's School of Medicine.
They tested the two diets on a group of 609 men and women, aged between 18 and 50, who followed either approach for a year. But they were instructed to ensure that what they ate was a healthy option: a soda drink might be low-fat, but it's not healthy, and an avocado was a healthier low-carb option than lard, said research team leader Christopher Garner.
At the end of the trial, average weight loss in both groups was 13 lbs (5.9 kg), although there was enormous variation among the individuals; some lost 60 lbs (27 kg), but others gained as much as 20 lbs (9 kg). Those who lost the most weight had changed their relationship to food, said Gardner, and were more thoughtful about what they ate. "I feel like we owe it to Americans to be smarter than to just say 'eat less'," he said.