Hey Irene:
My mum is a retured SW consultant, and she agreed that you're allowed 19 units a day. Any more questions, let me know. She's been a consultant for 12 years, and only retired a few weeks ago so she's pretty clued up!
The first time I did fast forward for 1 whole week, I lost 10lbs! I've since been doing it for 3 days at a time, to get back on track, and found my weight loss going between 3 and 6lbs.
I'm currently doing regular food optimising, one day of red, two green (I'm semi veggie so my choices are limited on a red day) but you'd get a strong weightloss on mix to max!
If a big weight gain has occured in a short period of time, I normally have little trouble getting it off providing I get back on the plan ass soon as possible!
Just joined the gym as well
Best of luck with FF, it can get tough but it's totally worth it! And don't be disapointed if you go to class and don't get an amazing loss, as it'd come off the week after if this is the case!