A 45-year-old man comes to clinic with a history of excessive bloating, foul-smelling flatus, and loose stools for the past several months. He notes that about 30–60 minutes after breakfast each morning, he experiences cramping, bloating, passage of smelly flatus, and a very loose, watery bowel movement. He has not seen any blood or mucous in the stool and denies any weight loss. This does not happen with lunch or dinner. Every day for breakfast, he eats a big bowl of cereal with milk and a yogurt smoothie. Physical exam is unremarkable with normal bowel sounds, no organomegaly, and no abdominal tenderness.