Although this is controversial, many experts do believe that low carb diets have a metabolic advantage.
In other words, that low carb diets increase your energy expenditure, and that people lose more weight than can be explained by reduced calorie intake alone.
There are actually some studies to support this.
A study conducted in 2012 found that a very low carb diet increased energy expenditure compared to a low fat diet, during a period of weight maintenance.
The increase was around 250 calories, which is equivalent to an hour of moderate-intensity exercise per day!
However, another study has suggested that it may be the high protein (but not low carb) part of the diet that causes the increase in calories burned.
That being said, there are other mechanisms that may cause an additional metabolic advantage.
On a very low carb, ketogenic diet, when carb intake is kept extremely low, a lot of protein is being transformed into glucose in the beginning, a process called gluconeogenesis.
This is an inefficient process, and can lead to hundreds of calories being “wasted.” However, this is mostly temporary as ketones should start replacing some of that glucose as brain fuel within a few days.
The bottom line is, low-carb diets appear to have a metabolic advantage, but most of it is caused by the increased protein intake. In the beginning of a very low carb, ketogenic diet, some calories are wasted when glucose is produced.