There are a million diets to go for if you’re looking to lose weight, but which is the right one? Chances are, it’s not the one you think — especially when it comes to carbs versus fat.

Nutritionists have long debated which should be cut from your diet if you’re looking to shed pounds, with some say that eliminating fat is best but other saying it’s carbs that pack on the pounds, according to a Washington Post report.

Low-fat diets were all the rage in the 1980s and 1990s, but in recent years, cutting carbs has become the central focus, with many even arguing that fats are fundamentally good.

So the National Institutes of Health decided it was high time someone took a deep look at the issue, and they did it in a somewhat unusual way, according to the report.

They examined 19 obese adults of about the same weight and body-mass index in an inpatient unit at the NIH clinical center over two-week increments. The volunteers were given a diet of 2,740 calories with a breakdown of 50 percent carbohydrates, 35 percent fat, and 15 percent protein, about the same as their previous diet. Over the next six days, however, the patients either received a low-fat or a low-carb diet, with both of them cutting calories by 30 percent, in addition to exercising one hour per day on a treadmill.

Then, they put them in a sealed, climate-controlled room with analyzing devices for five days to see the results. They watched the carbon dioxide and nitrogen that was being released and their hormone and metabolite levels.

Which one? Sorry, low-carb fans: low-fat diets win this round. There was a minimum detectable difference in the cumulative fat loss of 110 grams, and the average participant lost 463 grams on a low-fat diet versus about 245 grams for low-carb dieters — that’s nearly twice as effective.