Dukan Diet - how healthy is it, really?

Firstly - 111 days and 15.5kg to go. To reach my goal pre-Xmas I need to lose an average of 800g per week. It's do-able, I know. I have been at this diet for almost 4 weeks. Weight loss - 3.5kg. Not bad.

I didn't blog yesterday because I was thinking, analysing and asking questions.
Here's the thing. I have been to the gym every morning this week - for around 45 minutes, twice with trainer Abi putting me through my paces. Results - sore ass (muscles), sore arms, sore legs and feeling quite heroic.
Here's the other thing. I have really stuck to the Dukan Diet - high protein, no carbs, no fat, three tablesoons of oat bran each day - every second day is JUST protein.
So here's the final thing. How healthy is it really to completely cut out carbs? (probably still getting some animal fats from protein, ie: cajun salmon steak for dinner last night). I have had a few bad headaches, and this morning while boxing with Abi I felt a little light-headed for a minute or two. She says some carbs are needed with increased exercise. And fibre - the oat bran did not 'move' me for four whole days until this morning. OK, I understand that there is less to move, but perhaps I am not eating enough? And how healthy is it to completely cut out fruit and many vegetables, such as carrots? Could one apple a day be that bad? (Ryan, I need your response to this).

I have done some reading and research. Most dieticians seem to he saying - moderation, portion control, three smaller meals plus two healthy snacks in between to keep the metabolism going. Drink water before meals to help with the 'full' feeling. This seems sensible but I must admit the Dukan system with clearly stated foods that are NOT allowed is easy to follow.

Conundrum. Do I ditch Dukan and follow something more balanced, like Weight Watchers point system? They have a cheap online program that helps you calculate daily points from foods and exercise. This would be easier than trying to calculate actual proteins, carbs and fats manually. It creates a food diary, which most experts say is important. If I switch to Weight Watchers do I still keep protein high and carbs low, but not totally cut out?

The one thing I do know is that I am totally committed to this journey. I want a little black dress for Xmas. I will stick with the gym. I will stick with a diet. But is the right one?