I do weight training 4 times a week in a fasted state and if anything i've got more energy. 'Energy' isn't released from food when you eat it..well it is, but it's far from optimal. Sympathetic neural activity and hormonal release associated with that (adrenaline, cortisol, glucagon etc) will all increase when your insulin is low and that's when you truly feel energized.

The only issue is reducing your reliance on the glycolytic pathway, that is immediate energy from ingested carbs and increase lipolytic and glycogenolysis (fat burning and stored glucose use).

Either way 24 hour fasts twice a week will be benficial for sure

Yeah i've seen that youtube guy and he talks sense.