This invention is a device and system for monitoring a person's food consumption comprising: a wearable sensor that automatically collects data to detect eating events; a smart food utensil, probe, or dish that collects data concerning the chemical composition of food which the person is prompted to use when an eating event is detected; and a data analysis component that analyzes chemical composition data to estimate the types and amounts of foods, ingredients, nutrients, and/or calories consumed by the person. In an example, the wearable sensor can be part of a smart watch or smart bracelet. In an example, the smart food utensil, probe, or dish can be a smart spoon with a chemical composition sensor. The integrated operation of the wearable sensor and the smart food utensil, probe, or dish disclosed in this invention offers accurate measurement of food consumption with low intrusion into the person's privacy.