Here's a popular rapid fat loss diet plan that I have used to coach people to get really lean. It is a simple way to get lean in a 2-3 week period without dropping muscle mass. The key is that you need to train at least 3-4 times per week to ensure no muscle loss.
Here is a simple outline of the diet.
[+] Drink a 30-40 gram meal replacement shake for breakfast.
[+] Drink a 30-40 gram meal replacement shake for lunch.
[+] Eat a salad for dinner with 1-2 chicken breasts and vinegar based dressing (I like rice vinegar).
[+] If you are especially hungry, eat an apple after dinner.
[+] If you are still hungry, eat a cup of cottage cheese before bed.
So, this seems simple right it just requires a little discipline and effort and the results should follow.