Why is it forbidden to eat onions and garlic during the festival/fasting?

Why is it forbidden to eat onions and garlic during the festival/fasting?

Dr. K K Aggarwal, President Heart Care Foundation of India and Group Editor in Chief MEDtalks, discusses the reason for not eating onions and garlic during festival/fasting in this video. During spiritual fasting, it is important to be in touch with inner conscience and be happy and experience peace. There is a shift from sympathetic to parasympathetic mode. He will explain the mythological importance behind it as onions and garlic are under-rooted which has to be avoided.