if you were eating 800 cal a day and went straight to atkins, you shouldn't have put on any weight. your metabolism picks up right away if you eat more food, there is no such thing as a rebound effect when you eat less calories and then start eating more. the only way you put on weight like that if you eat excessively and lots of "bad" food.
at least you've come to senses
i've been on induction so many times before i got it right and my tastes changed. i never ate meats before atkins, so it was terrible for me to adjust my diet.