Strictly limiting carbohydrates and eating more fat may help the body burn more calories, a new clinical trial shows, according to CBS News.

Researchers found that among 164 adults in a weight-loss study, those placed on a low-carb, high-fat diet burned more daily calories, versus those given high-carb meals. On average, their bodies used up 250 extra calories per day over 20 weeks.

The researchers estimated that over three years, that would translate into an additional 20-pound weight loss for an average-height man.

"This study refutes the conventional thinking that it's only calorie-cutting that matters," said senior researcher Dr. David Ludwig. He is co-director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital.

Instead, he said, the source of those calories may make the difference in whether your metabolism "works with you or against you."

According to Ludwig, the findings support a theory called the "carbohydrate-insulin model." The premise is that diets heavy in processed carbs send insulin levels soaring, which drives the body to use fewer calories, and instead store more of them as fat.

"Our study suggests that you'll do better if you focus on reducing refined carbohydrates, rather than focusing on reducing calories alone," Ludwig said.

He and his colleagues reported the findings online Nov. 14 in the BMJ.

Many studies over the years have attempted to answer the question of whether low-fat or low-carb is better for weight loss. Often, they've concluded there is little difference.