K.I.S.S.. The idea is to keep the muscle mass, and to even increase it some, while losing body fat. Calorie reduction (lower than the amount required for body repair and maintenance...mean average around 3,200 unites daily) can feed on muscle mass as well as the body fat it's self. Those less experienced BB'er who "diet" down for a contest wind up looking like muscless skinned rabbits. Extreme calorie reduction and cardio go hand in hand as the major cause.
Might consider dropping the carbs to a lower daily range. Carbs are a ready energy supply, among other things, for the body. Reason endurance athletes carb up before an event(not the only way but the most commonly used method). Body's first choice, when the carb source is less, is to use body fat as it's first energy supply response.
Can start with 80 to 100 grams of carbs a day, to see how your body reacts. Each of our metabolism's are different, so begin with the higher amount first. Generally it is within the 40 to 60 grams a day ration. Try not going below the 20 gram mark. Many of the Pro's do, but they are chemically engineer to handle just about anything. But for brief periods in their training.
Do buy a carb counting booklet and also read up on the subject more for a better understanding of the effect of this type of diet. Plus hints on how to arrange it to your life style; eating out, party's, etc. Rather than a 7 day a week eating plan, there are different approaches. Some will keep on it monday through friday and on the weekend cheat a little which might include pizza, burgers & fries, etc. But do not pig out. Keep it on a moderate level. Also the 6 day a week thing, with one day off (usually saturday or sunday) that week.
Use this type of protocol on athletes all the time, if making bwt is needed for an event. Keeps their energy and strength up during this period. And the muscle mass. Fat seems to melt away on most. Actually user proper carb management to add muscle mass with much less fat.
Throw in interval training , 2 to 3 times a week, for notching up the fat lost. Along the lines of what Montague advised. Personal view only; 45 to 60 minutes, either 4 to 7 times a week, is just madness for any serious BB'er or lifter. Good Luck