Hi Sarah... That's my problem... Last year I did a diet (800 calories per day) and without exercise I lost 30 pounds in 3 months but 6 months later I gained back 45!!!! So... I start again one month ago... eating 1200 calories per day, walking 1 hour per day and I lost 20 pounds already!... the amazing thing is i don't feel hungry anymore and with the exercise I have a lot of energy now.
Don't jump off the wagon just take your time to lose weight, the transformation in not gonna happen tomorrow.
Good Luck