"Am fat city" is a phrase that means you are in a favorable or advantageous position. There are many synonyms that can be used instead of this colloquialism to convey the same meaning. Some of these synonyms include "in the lap of luxury," "on top of the world," "riding high," "living the dream," "on easy street," "in a good place," "on the gravy train," "in clover," and "in seventh heaven." Each of these phrases is commonly used to express a feeling of abundance, success, and comfort that one may experience in life.