If you are looking to do cardio to lose fat but not muscle, it's a delicate balance. If you've been working out your muscles are in fact cut and toned, but jut covered up with body fat. Most people don't use the right techniques so they end up losing muscle along with the fat. More cardio doesnt always mean getting more cut. Honestly if you do cardio properly, you probably wont even have to change your calorie intake (smaller portions).

Try this:

High Intensity Interval Training.

Basically its 3 stages. Warm-up, intervals and cool down.
(level 1 is little exertion on your part and level 10 is all out)

Warm up for 2 minutes on about level 5.

Then you do 8 minutes of the Interval running, where you switch from about a level 8 for 20 seconds to to a level 5 for 10 seconds. this works tons easier if you are running insted of treadmill. then just repeat the cycle for a total of 8 mins.

Cool down is 2 minutes back at level 5.






Its good to start at this 2 - 8 - 2 cycle, but when you get used to it change the intervals to a longer period. Insted run a 2 - 12 - 2 or something like that. Just don't do more then 20mins of cardio a day. It gets less effective and can be negative after 20 mins.

If you are doing your cardio on teh same day you go to the gym, do it after the workout. Another tip is if you are running or doing cardio at a different time or entirely different day then your workout, do it before breakfast. Its supposed to be the most effective time to burn up the fatty acids.