At new year I was 203lbs and unfit and decided I needed to lose some fat so I turned to Kinect and...
Kinectimals 1000/1000 ~ really very good with some good gentle exercise. A showcase for Kinect and probably it's most polished title. Got for my bairns but got quite into it myself!
Kinect Adventures 1000/1000 ~ again you can build up a real sweat if you put the effort in to get Golds and Platinums; use the achievements to keep you motivated.
Dance Central ~ Really good exercise and makes you move
Your Shape ~ Burnt 2000 cals off, mostly with a daily couple of Cardio Boxing routines and some Zen yoga cool downs.
And I'm now currently 6 sessions into the 9 week program on EA Sports Active 2 on medium and I now find I actually look forward to the 30 odd mins of exercise.
...And as of this morning I'm 181lbs; 22 lbs down and I feel great. My heigh it 5'10'' so I'm finally into the 25's BMI and people are commenting all the time that I seem to have lost weight.
Of all the titles I currently prefer EA Sports Active 2 as it's the one that really pushes you the most though at the fitness level I was at I'm glad I started with the earlier titles. It's only problem is it's use of Kinect can be a bit cluncky at time but overall it doesn't detract too much from it's purpose.
I'm also adding a little Sonic Freeriders, Kinect Sports and Dr Kawashima's Body and Brain into the mix; as someone who really only used to play 'hardcore' titles you could argue I'm now a bit of Kinect Fanatic.