Final answer:
Juan's overeating at his grandmother's house on holidays is most likely influenced by emotional and cultural factors, which include familial and cultural traditions around holiday meals, as well as the pleasant social setting.
Step-by-step explanation:
If Juan usually overeats at his grandmother's house on holidays, the factors most likely influencing his food choices on those days are a) Emotional and cultural factors. These include the psychological impact of being in a pleasant, familial setting which can increase one's consumption of food, as well as the cultural traditions that often come with holiday meals. Juan may be experiencing the influence of family traditions and the cultural significance of certain foods, which can overshadow other factors like health or dietary restrictions in the context of celebratory occasions.