Eating only a small amount; having a small appetite or low food intake, often used about people who don't eat much.
うちの子は食が細くて、いつもおやつでお腹がいっぱいになってしまう。
My child has a small appetite and always gets full from snacks.
年を取ると食が細くなる人が多い。
Many people tend to eat less as they get older.
彼女は食が細いので、外食するときは小さい盛りを頼むことが多い。
She has a small appetite, so when we eat out she often orders smaller portions.