I don't claim to be a nutrition or fitness expert but as is the case with most of us i've done a lot of research and followed a lot of bad advice which i feel has interfered hugely with my success. Soooo I wanted to pass on the knowledge i've gotten from the experience:
when you first embark upon a weight loss regime it's hard to sort out the facts from complete nonsense and it's widely accepted that women should eat between 1200-1400 calories a day. For starters this strategy is nearly impossible to follow for very long, and secondly your body will probably think it's starving and cling to every bit of fat it can get, not to mention your metabolism will slow down drastically.
the best way to prevent this from happening? Know your resting metabolic rate (the amount of calories your body burns to survive). This number alone will probably exceed 1200 calories a day and that's not including the calories you burn doing things like walking, eating, showering, brushing your teeth or exercising. Truth be told, most women need to get at least 1600-1800 calories a day, more if you work out.
There are tons of resting metabolic rate calculators on the internet, find out what yours is and make sure you're not eating too little.