In the research, 19 obese adults were closely monitored in a ward for two 2-week periods. During their time on the ward, every single morsel of food eaten was monitored and controlled. In the first two-week period, 30% of their calorie intake was cut through carb restriction, with fat intake remaining the same. In the second two-week period, the variables were reversed.
And now the important bit. It was found that on the low-carb diet, the participants lost an average of 245 grams (0.54 pounds) of body fat. On the low-fat diet, they lost 463 grams (1.02 pounds).
“A lot of people have very strong opinions about what matters for weight loss, and the physiological data upon which those beliefs are based are sometimes lacking,” said lead author Kevin Hall, from the National Institutes of Health, in astatement. “I wanted to rigorously test the theory that carbohydrate restriction is particularly effective for losing body fat since this idea has been influencing many people’s decisions about their diets.”
However, he cautions against anyone making dietary decisions based on this research just yet, not least because of the limited sample size – 19 people – of this study. Further research, though, could continue to fuel the flames in one of the great dietary debates.
“We are trying to do very careful studies in humans to better understand the underlying physiology that will one day be able to help generate better recommendations about day-to-day dieting,” added Hall in the statement.
But as Professor Susan Jebb (not involved in the research) from the University of Oxford pointed out to BBC News, “the best diet for weight loss is the diet you can stick to. All diets ‘work’ if you stick to an eating plan that cuts calories, whether from fat or carbohydrate, but sticking to a diet is easier said than done, especially given the prolonged time it takes to lose weight.”