The most effective method I've used for losing bodyweight while maintaining lean muscle mass is the warrior diet, combined with kettlebell training.
The warrior diet is rather unconventional but the results speak for themself.
As far as kettlebell training, I would recommend performing all excercises in a high intensity interval format, and also lift heavy(compound movements such as squat, deadlift, dips, pull ups) 2-3 times a week on top of kettlebell training.
For free tutorials and workouts please check out my website at
For the warrior diet, you can get the book here, its really worth it, no other dieting method has worked so well for losing body fat.