Henry:
If you're running for two hours, at whatever pace, you're transforming your body into a calorie-burning machine. Your metabolism is elevated for several hours after such a run. The key to losing weight, apart from drinking a lot of water and making sure that you're getting enough protein to rebuild worn-down muscles, is finding a way of taking in enough carbs to replenish your glycogen stores while maintaining a modest net calorie deficit.
I tend to think that one meal a day makes this whole process more difficult than it needs to be, so I'd advise you to modify that.
What I'd suggest, actually, is that you make your biggest meal of the day the one you eat during the hour or two after your longest daily run. Obviously, for maximum glycogen replacement, you need to get some carbs in you within half an hour after you finish that run. In the summer, after runs lasting two to three hours, I threw down a quart of Gatorade right after I came through the door, followed about fifteen minutes later by a fruit smoothie: yogurt, banana, fresh or frozen strawberries, honey, a little strawberry jam, juice of one lime, orange juice, and a tray of ice cubes. Blend this up for about 60 seconds on "high." This did the trick.
An hour later, when I'd regained my appetite, I'd have a real breakfast: eggs, toast, maybe sausage. A bit of fat is a good thing at this point, since it slows digestion.
Now, that particular regimen--Gatorade, followed by a smoothie, followed an hour later by breakfast--pretty much took care of my glycogen stores.
If I were trying to lose weight, I'd do exactly the same thing. A two-to-three-hour run can take care of all that food. But I'd then carefully monitor what I had for the rest of the day. In your situation, I'd probably have a snack of some sort about three hours after that breakfast, and I'd have a big salad for dinner with chicken strips on top for extra protein. Just a solid, reasonably low-fat dinner, with some kind of portion control: chicken (not fried!), salad, potato, or a couple of pork chops, sweet potato, and green beans.
I'd stay away from
*) potato chips and other devour-the-bag snacks
*) desserts of any kind, apart from a couple of cookies
*) noticeably fat-heavy foods, such as cheesecake, greasy meat, etc.
*) beer! Have no more than one beer, max. Or one glass of wine. Beers are 150 calories apiece. Three beers and you lose no weight that day.
I'd snack on carrots and celery sticks, with a few triscuits (basic low-fat carbs) thrown in.
The key to losing weight with this kind of regime is NOT going to bed with a full stomach--unless the stomach is filled with low-caloric density foods, such as salad or broccoli or carrots. The key is to have the big meal of the day early enough that by the time you go to bed, you're very slightly hungry. That very slight hungriness is the beginning of your net caloric deficit, and that's precisely what you want to be cultivating.
Of course, if you go to be too hungry and you try to run long in the morning, you may find yourself running out of energy. But only you can determine if this is true. It may not be true for you. Some runners--and I'm one of them--can do just fine on an empty stomach. As long as you've taken care to replenish your glycogen stores as I've described above, you should be fine.
So rather than one meal a day, I'd say: one big meal a day, during the hour or two after your longest run, and one or two smaller meals whenever you need them.