A goal to lose fat and gain muscle is only possible in extremely rare cases and with genetically gifted athletes. For the majority of clients who desire to gain muscle they must be in an excess of calories but to drop body fat they must be in a deficit of calories. In most cases we would design a program to drop body fat first. It is much easier to drop body fat than gain muscle. A lean body is going to grow more efficiently than a heavier body. Calories would be designed for the scale to drop. Once you are happy with your body fat percentage calories would be slowly increased so that muscle mass starts to increase.