You will never achieve a positive nitrogen balance with a low calorie diet. It takes raw materials - carbs, protein and fats - to build new muscle mass and support recovery. Increasing your calories by 50% (from 3,0000 to 4,500 per day, for instance) for three days can spur growth while adding little if any bodyfat. The key is to limit the increased calories to a designated three day period; you'll be able to stimulate growth by improving muscle sensitivity to insulin and by providing more carbs for glycogen storage.
If you are in a overtrained state - and if you're not gaining any new muscle mass, this is probably the case - the additional calories will promote anabolism before fat storage is able to kick in. That's why you want to limit the 50% increase to a three day period. After that time, return to your typical intake of daily calories; you'll have stimulated new growth without adding unwanted fat.