i dont think 75 min is that much sgt. a couple months ago, i was playing 4 times per week for 1.5-2 hrs each time. i like tennis bc its kinda similar to interval training where you are basically sprinting for short period and then resting inbetween volleys. i love tennis for cardio and i don't think it matters what type of cardio you do for fat loss. i switch up my cardio routine all the time from biking, eliptical, treadmill, jumprope, tennis. just make sure your doing it 3-5 times per week. but i think your diet is more important than cardio so make sure that is in check first. good luck