An improved sensor (102) for calorie monitoring in mobile devices, wearables, security, illumination, photography, and other devices and systems uses an optional phosphor-coated broadband white LED (103) to produce broadband light (114), which is then transmitted along with any ambient light to target (125) such as the ear, face, or wrist of a living subject. Some of the scattered light returning from the target to detector (141) is passed through narrowband spectral filter set (155) to produce multiple detector regions, each sensitive to a different narrowband wavelength range, and the detected light is spectrally analyzed to determine a measure of calories, such as calories expended, calories ingested, calorie balance, or rate of calories expended, in part based on a noninvasive measure of respiration, such as respiratory rate, respiratory effort, respiratory depth, or respiratory variability. In one example, variations in concentration in components of the bloodstream over time, such as hemoglobin and water in the arteries, are determined based on the detected light, and the measure of respiration is then determined based on the variations in concentration over time. In the absence of the LED light, ambient light may be sufficient illumination for analysis. The same sensor can provide identifying features of type or status of a tissue target, such as heart rate or heart rate variability, hydration status, sleep state, or even occupancy counting. Calorie monitoring systems incorporating the sensor as well as methods are also disclosed.
