Passing stool soon after eating can be due to an overactive gastrocolic reflex or conditions like Irritable Bowel Syndrome, especially if it happens frequently. Focus on eating small, regular meals that are easy to digest, include protein (eggs, dal, curd), healthy calories (nuts, banana, rice, ghee), and avoid very spicy, oily, or processed foods that can trigger bowel movements. Stay hydrated, eat slowly, and try to manage stress, as it can affect digestion. For weight gain, increase calorie intake gradually with nutritious foods rather than junk food. If symptoms persist, worsen, or are associated with loose stools, pain, or weakness, consult a doctor for proper evaluation and guidance.