Welcome to the forum. We are very similar except that you are about 9 years older than me. I am about 450, male, and work in the Computing Industry.
1) Start a journal. Record exactly what you are eating each day. You are going to have to start to count calories to be sucessful. If you need information on starting a journal it can be found:
Starting a Journal
I also recommend getting a diet software package that will help you 1) record exactly what you eat 2) record exercise 3) help you remember and track water intake. I use Diet Power which runs about $40-45 US.
2) Determine your Base Metabolic Rate(BMR) to find out how many calories per day you need to consume. This may be completely against what you currently think about eating but the bottom line is you probably need to eat more to loose. There are a number of tools to use to compute your BMR. First, there is a fast calculation method (10-12 x' your current weight). Let say for you it's 10 x 450lbs = 4500 calories. There are several other formulas Including the Harris-Benedict Model. Here is a link to a page that will provide that calculation:
Harris Benedict BMR Calculator
I ran your numbers through this model and I came up with 3953 calorie per day BMR.
These calculations show you need between 3900 and 4500 calories per day to maintain your current weight. Now, rule of thumb says you need to reduce your calorie intake 500 calories per day to loose a pound per week. I would not exceed a goal of more than 2 pounds per week, because more would not be healthy, and would probably cause your metabolism to slow down to far. This means that 1000 calorie per day reduction might be your goal. Therefore if we take 3900 calorie BMR and subtract 1000 we get 2900 calories per day as your target daily calorie intake.
Next, we look at your consumption balance between protein, fat, and carbohydrates. Again there are a number of ways to compute your ideal requirement. General rule of thumb says:
Protein 25-30% Total Calories
Another method is to multiply your weight in pounds by (.6-.8). I suggest .6 in this case. One more which I like personally is 1 gram of protein times your Lean Body Mass(LBM) in pounds. Now computing your LBM, may not be easy but for me for example the lowest weight I'd ever been in my adult life is 235lbs. At that weight I was probably about 15% body fat. That means 235lbs x .85 = 200 pounds would be 0% body fat.
So assuming you are similar bone structure-large, and weight, and height as me, we take 200lbs as your LBM times 1 gram/pound = 200 grams of protein per day minimum. Since protein is 4 calories per gram we get 200 grams x's 4 calories/gram = 800 calories per day protein.
Next we subtract 800 protein calories/day from 2900 target calories per day = 2100(fat calories + carb calories) calories. Next, if we give you 25 calories of carbs(ok, Atkins purest will save 20 calories of carbs, but 5 calories is not going to make or break ketosis) we have 25 carb calories times 4 calories/gram for carbs = 100 calories per day carbs. Subtracting this from 2100 calories we get 2000(fat calories). 2000 fat calories divided by 10 calories/gram fat = 200 grams of fat per day.
Now lets see how these number compare to guidlines:
800 Protein Calories = 800 calories /2900 target calories = 27%
2000 Fat Calories = 2000/2900 target calories = 68%
100 Carb Calories = 100/2900 target calories = 3.4%
As you can see this is very close the guidelines for recommend ratio intakes. I am not saying this is exact but should be a good approximation.
3) Try to spread your calories out into 5-6 meals per day. A suggestion is eat every 3 hours. Breakfast, mid-morning snack, Lunch, mid day snack, dinner, evenging snack. Spreading meals out will help stimulate your metabolism.
4) Drink more water. Someone at your weight should be getting a gallon of water in per day. Yes, I said one gallon per day. My plan of attack on water is as follows: 30 onces before I leave the house in the morning (yes, you will probably have to go to the bathroom every 20 minutes starting an hour later, but think of it as good exercise). Get a water bottle at your desk, and just starting siping it. I try to get two 20 onces bottles of water down while at work. When you get home, another 30 onces before dinner. After dinner, another 30 onces. That adds up to 30 + 20 + 20 + 30 + 30 = 130 onces.
5) Exercise. Start slow, but do something. Walk a block out and back 3 times per week. Each week, pick up the pace a bit. If you have access to a decent gym I recommend an eliptical trainer or a stationary bicycle.
6) Learn everything you can about Metabolism. What you will find is that winning this battle against obesity requires you understand how your body processes food, how exercise impacts metabolism, how and what to eat to help your body burn fat. Get and read some books on this stuff. Trainerdan on this forum in the exercise section has a very good book on Metabolism. I highly recommend it:
Trainerdan Metabolism Book
7) Be patient, set a plan, set reasonable goals, ask questions. There's a lot of people here in the same boat as you are. There's a ton of very good information here.
Well, that should get you started. Welcome again, we are here to help so get your journal started. Look forward to seeing you around.