Genetics probably. Some people are suited for endurance sports, others gain muscle more easily. I recognize myself from the description. Very hard to gain muscle/weight and eating enough feels like a chore.

These are all fast breakbeat rhythms. Drum and bass music is generally broken beats (as in not 4-to-the-floor) in 160-200 bpm tempo range with emphasis on drum and bass elements. There are a lot of subgenres with specific nuances.