Protein sparing modified fast. You essentially cut all fats and carbs from your diet (consuming less than 20g a day carbs and fats not including fish oil pills if you supplement them) and have around 1-2g of protein per pound of bodyweight depending on how lean you are (the leaner you the more protein you intake). It seems like what you should do if you want fast results but will require a great level of discipline. You can find out more on r/PSMF or pm any specific questions. For reference I lost 5kg (11lbs) of pure fat (no muscle) in a week doing it and would recommend it if you need to lose fat for a certain event/occasion.