To lose body fat i read you have to do weights aswell as cardio. Is it heavy weights tho will 6-8 reps or a light weight where you can do quite a lot?

[removed] doing a lot of reps (15-30) does not result in more fat loss than lower (yet still moderate -- 10 is a good number) reps with progressively higher intensity. if anything it burns less fat, since you are not gaining muscle (which require more calories and oxygen to sustain)