Only strenght training and pilates (+flexible eating)?

Hi everybody,

I've been doing strenght training regularly for about 2-3 weeks now. Before that I did pilates work-outs for a half year. I was wondering if HIIT and cardio work-out are really 'necessary' for a change in fitness and health (also less body fat percentage). I'm trying to keep the schedule of 2 lower and 2 upper body work-outs each week.

What are your thoughts/experiences on this matter?

Do you guys think HIIT and cardio's are something you shouldn't skip?

Thank you for reading this!