Eating one meal a day is probably the worst thing you could do. Not eating slows down your metabolism (I am not scientist, but your body is probably trying to ration your nurtrients so that it doesn't run out due to lack of food).
Instead of 1 huge high calorie meal, why not 6 small low calorie meals. Maybe something like
breakfast: oatmeal and 2 egg whites
(2-3hrs later) in-between meal: maybe some low GI fruit (grapes, and apple, ect)
(2-3 hrs later) Lunch: tuna on a whole wheat bread
(2-3 hrs later) in-between meal: maybe some more fruit or some green veggies
(2-3 hrs later) Dinner: a small salad, some type of meat (salmon, steak, chicken breast), and side of green veggies
(and hour or so before you go to sleep) last meal: a serving of fat free cottage cheese
this is just an example, and on workout days you can substitute one of those meals with a protien shake for either pre or post workout (like you workout 2 hours after lunch and drink a protien shake within the hour)
I don't know your schedule so keeping with that format might be hard, but like I said eating one big meal a day is not the way to go.
Finally, do a lot of cardio (runnning, jumping rope) to help burn the fat off quicker.
Good Luck with your diet, I know how hard it is...also if anyone want to make some correction to my sample eating plan go ahead.
EDIT: oh and btw I used to have a bit of trouble losing weight and keeping it off, but once I started eating right and upping my cardio the pounds started to come off. Don't get discouraged and start going off your diet and you should be fine.
I think the number one cause of people putting back on the weight they lost is because they always revert back to their old ways
"Oh, I have been good this week, I can have an extra slice of this 500 calorie cake."
then the next thing you know they are on an infomercial(sp?) for the newest diet craze
"I have tried all the diets on the market. They all worked, but the weight would always come back. On the *insert fad diet here* I last 100 pounds and have kept it off for weeks now!"
EDIT #2: Don't forget to drink a lot of water (not juice or soda...WATER) not only is it the only liquid you ever need, but it supresses your hunger and helps you to not run out and start eating junk. Usually I drink a bottle with every meal.
The best way to know you are drinking enough water is your urine. If it is dark then you are dehydrated. If it is very light yellow (or in my case clear) then you are well hydrated.
