I can't speak scientifically, only what worked for me. I was in the same boat, not as big but was 285 at 6'1 and definitely more fat than muscle.

I lifted everyday in the mornings and immediatedly after went for my cardio session. I know it isn't 'proper', but since I used to be a good sized guy (237 at 7% bf) I wasn't really too concerned about a little muscle loss.

I started with long walks, about 45 minutes to an hour. I was just too big for running. I tried but in a few days the shin splints were killing me. After a few weeks I started doing sprints on a soccer field, about 10-15@ 60 yards. It was brutal at first but my body adapted fairly quickly. I lost 30 lbs. in my first month. At no time during this did I ever take a supplement or protein shake, just all raw veggies, fruits and lean meats off the grill.

The second month I added a shake a day but upped the cardio. I lifted as heavy as I could to keep up my strength, but my primary focus was still weight loss. Second month I lost 15 lbs.

The third month I started a more bodybuilder type routine in the gym, added in the supplements and shakes and was in good enough condition to really push the cardio to the point I thought it might be wise to keep an ambulance handy just in case. I lost another 15 lbs. I got down to 227 in 3 months, could see my top 4 abs (not great for most but a miracle for me) and felt great.

The only help I had was that I am prescribed 200 mg of test cyp a week which obviously kept me from losing too much muscle mass. If you can I would definitely add it in as it helps with recovery because us fatties need it.

Hope this helps and feel free to adapt it to your own personal time table and abilities. Just keep focused and I know they say don't weigh yourself, judge results in the mirror. Bullshit. I stepped on that scale about 10 times a day to hold myself accountable for every calorie I took in and everyone I burned.