FWIW I don't think 5 hours a week is a lot of exercise. There are 168 hours in a week.
Our bodies aren't designed to be sedentary. I enjoy HIIT but research in to the effects of being sedentary suggest that short exercise sessions don't outweigh the effects of long periods of inactivity on our health. Movement throughout the day is important for our health. Boffins who have been researching 'sitting disease' suggest that we need to move throughout the day.