A method of treating diarrhea or an inflammatory condition of the gut in a subject comprises administering a therapeutically effective amount of beta-hydroxy-beta-methylbutyrate (HMB) or a salt thereof to a subject in need thereof. A method of treating secretory diarrhea in a subject comprises administering a therapeutically effective amount of HMB or a salt thereof to a subject exhibiting one or more of the following symptoms: loss of fluids from the gut, loss of electrolytes from the gut, dehydration, or inflammation of the intestinal tract.