When suggesting a fitness routines for people who want to lose fat I don’t recommend more than 2 hours of steady state cardio a week.
However, this is not enough and needs to be complemented by doing strength training 3 times a week.
Many people make the mistake of doing ONLY cardio for hours and hours and lose lot of lean muscle in the process.
If you have good fitness levels you can completely replace steady state cardio with HIIT. Then you will only be required to do 2–3 sessions of HIIT, 20 min per session.
Overall, 3–6 hours of TOTAL activity is MORE than enough to achieve any goal.
If you want to know the science behind creating your own workout plans I have created a FREE Fitness for Beginners course which you can enroll here.
Hope this helps:)