Are you being served? Managing waist and waste via serving size, unit size, and self-serving

•While consumers who are served food in smaller units consume less, they waste more.•Consumers who serve themselves food in smaller units consume less and waste less, without lessening consumer satisfaction.•The effect of serving size on consumption and waste is not moderated by unit size, irrespective of whether consumers are served or serve themselves.•Self-serving food in small units as a win–win solution for reducing waist and waste.