In meanning,there is no difference.It just like the sentences"我渴了"and“我口渴了”.They are the same.

台灣人最愛說 “肚子好餓囉~ ” (^_^)

no difference in meaning,but "我饿了”is more brief.

“我饿了”is simplify from "我肚子饿了“

中国人常说“我饿了”，不说“我肚子饿了”。