A system is provided that includes a portable measurement device for measuring acetone in a breath sample of a user. The measurement device comprises a housing, a user-direct breath input device for engaging in direct fluid communication with a respiratory tract of the user and receiving the breath sample from the respiratory tract, a flow path disposed within the housing, a nanoparticle-based sensor disposed in the housing in fluid communication with the flow path and at an intermediate location between the upstream end and the downstream end, and a flow control device disposed in the housing and in the flow path between the upstream end and the nanoparticle-based sensor that prevents flow of the breath sample in an upstream direction opposite the downstream direction.