Control metabolic, dark period

Other techniques have been developed to avoid these timing-versus-accuracy problems using masks or canopies instead. This is often used for short term measurements or for critically ill persons [26,27]. But wearing such masks or laying under a canopy is not very convenient. It can not be expected from healthy subjects for more than about 8 h. Metabolism is largely controlled by many rhythmic stimuli like daily meals, sleep and even dark-light cycle. This creates the need to perform measurements over very long periods, best at least a full day. There are approaches like the factorial method to employ mask calorimetry for the estimation of the 24 h EE. A full determination of the 24 h EE and its actual rhythmicity however can only be fulfilled with chamber calorimetry. 

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