Abstract: Methods, apparatuses and systems of monitoring energy expended by an individual are disclosed. One method includes sensing, by a motion sensor, motion of the individual, identifying a plurality of activities performed by the individual over a period of time based on the identified motions, estimating, by a processor, energy expended by the individual for each of the plurality of the plurality of identified activities, and estimating energy expended by the individual by summing the estimated energy expended for each of the plurality of activities.