The term "bellied" usually refers to a rounded, protruding belly. Its antonym would be a term that describes a flat or concave belly, such as "hollow-bellied" or "sunken-bellied." Alternatively, antonyms for "bellied to" could be terms that denote a loss of weight or a reduction in belly size, such as "slimmed down" or "toned up." Other antonyms that might be appropriate could include terms such as "receded," "contracted," or "shrunken." Ultimately, the most appropriate antonym for "bellied to" will depend on the context in which the word is being used.