I used to be 300 lbs , I went down to 185 and then put on about 15 pounds of muscle.
I wouldn't recommend directly jumping into a CKD or TKD but I would recommend to *start* cutting down on the sugar and starch food products, totally cut out unnecessary sugars like soda and iced tea and such ( switch to diet ) that's the best first start, drinking more water and switching off any sugar loaded drinks. The carbs in one can of soda is almost twice my daily intake of carbs.
So that should start you off in the right direction. It's often very difficult to drop sugars completely, you have to do it gradually so you can follow the diet when you jump into it. Try to get into eating healthier carbs like oatmeal, brown rice and yams.
Diet doesn't do it all though, you need to exercise as well, if you are 315, I wouldn't be concerned about loosing muscle at this point. Start doing some cardio in the morning and evening. You need to get your body to use your body fat for fuel, which means you have to cut off the main fuel source which is carbs.
Once you get into the zone and are comfortable controlling your carbs and switching to healither foods you can start a more dedicated type diet like the CKD or TKD
Well hope my two cents helped
Ryan