I never knew working out twice a day was a proper programme! I did this a while back once a week when I had a job that got in the way and meant I had to cut my workout in two.
I did find it had a knock on effect for the following days I would workout. It made things feel harder- I found I got better results with a longer session then with 2 shorter sessions- not on a day to day level, but in the longer week term. Say I worked out every day sunday, monday, tuesday, wednesday, friday and took the thurs and saturday off, if I worked out once day I could manage this, but if I worked out twice on say tuesday, then wednesday-fri would feel harder and by the time I got to friday I just wasn't able to workout properly and it'd be better to have taken a rest day. It has a knock on effect, even if its just halving the exercise (so still doing the same time/calorie burn/exercises/whatever way you monitor yourself) But thats me, maybe see it and if it works with you, go with it. But from what I understand of weight loss you will need to keep it up until your done losing weight. Personally, once a day is more then enough for me!
But don't forget that exercise can only count for so much, food intake seems to count for much more. Do you weigh and measure everything you eat? or guess by eye? do you keep a log of everything you eat? it can help to do this if you are not already doing so.