The “energy deficit” idea is mostly speculative. Research shows stuttering is a neurodevelopmental condition with genetic components / predispositions. It is not a simple matter of running out of glucose or blood flow in Broca’s area. Imaging studies on brain perfusion are mixed. Some found reduced flow, others found no difference. i.e. There is no solid evidence to support the energy deficit idea. What is well-established is that many stutterers are often fluent when truly alone because there’s no sense of being judged. Controlled studies show stuttering basically disappears when speakers believe nobody can hear them. That points to a social-perceptual trigger, not an energy shortage.