A sensor system detects hand-to-mouth behavior. The system includes an electrical bio-impedance spectrometer and an inertial measurement unit. The sensor system may be worn on the forearm. The sensor system recognizes hand-to-mouth behavior in real-time, facilitating monitoring and immediate interventions An electrode positioning strategy optimizes the device's sensitivity and accuracy. Machine learning algorithms are leveraged to infer the hand-to-mouth detection. A prototype of the sensor system achieves 92% detection accuracy for recurrent usage by a single user and 90% accuracy for users that have not been previously encountered.