Hi Sue. Welcome to the forum.

To answer your question, no, it's not unrealistic to think you can lose 50 lbs in 7 months - it is however to think you can lose it in 3 days

If you've tried dieting in the past, and more specifically have tried LC in the past your body is probably thinking "Oh no, not again - hold on to that fat and water, she's doing it again guys". Yo-yo dieting, especially calorie restricted dieting, equals muscle loss and suppressed metabolism. You need to give it more time. It's going to take 7 months (or more). You need that time to learn how to eat all over again. This is where you learn behaviours and skills that will enable you to keep the fat off once you reach goal.

Advice:

Eat enough food
Eat your FAT
Drink your water

And enjoy your new WOL
Nat