The invention pertains to the establishment, implementation and management of a personalized information system pertinent to a user's general health, wellness and/or sport performance. A set of portable device with calorimetric, metabolic sensing, computing and communication capabilities are used for real-time measurement and display as well as long-term logging of highly accurate information about a user's metabolic state. In an aspect, the invention comprises a portable and hand-held indirect calorimetric device with the capacity to obtain the metabolic parameters of a subject by analyzing the composition of both inspired air and/or expired air of the user.