Low carb diets can help reduce fat rapidly particularly for endomorphic bodytypes who don't tolerate carbs well however as another poster mentioned are not sustainable at high activity levels over the long run.You can up the carbs moderately in line with activity levels and still lose fat at a more moderate but sustainable rate as long as there is at least a slight calorie deficit (consumed vs. expended).Also muscle gain is actually much easier with adequate carbs as you want at least a slight calorie surplus to put on muscle.