Atavism, as referred to here, is not an instantaneous change that happens overnight, but rather a gradual and progressive process. Much like the evolution of Uchiha Chi's Sharingan, which also falls under the category of atavism yet differs in certain ways; Uchiha Chi's atavism was accompanied by a degree of mutation, creating a distinction between his situation and Hinata's. By comparison, Hyuga Hinata's atavism is pure, entirely free from the interference of any other factors.
However, because Hyuga Hinata is still young and her physical development is not yet fully mature, she needs to consume a massive amount of energy to support the smooth completion of this atavistic process. Consequently, she must ingest a large volume of food to meet her body's demands.
In contrast, because Uchiha Chi possesses an extremely high quality of chakra, he can easily cope with the energy demands brought about by this evolution. Therefore, although completing the evolution still requires a certain amount of time for Uchiha Chi, he does not face the tremendous pressure regarding energy supply that Hinata experiences.
Chapter 311