Explain the term Direct Calorimetry?

Calorimetry refers to the measurement of the amount of heat evolved or absorbed in a chemical reaction, change of state, or formation of a solution. Direct Calorimetry is the method, which monitors the amount of heat produced by a subject placed inside a structure large enough to permit moderate amount of activity, These structures are referred to as whole room calorimeters. This method provides a measure of energy expended in form of heat, but provides no information on the kind of fuel being oxidized.

Further, this method is limited by the high cost and by the confined nature of the testing conditions i.e. the physical activity within the chamber is limited and therefore not representative of free-living environment. Another method to be considered is the use of a respiration chamber or of a direct calorimeter. To obtain reliable data with either of these techniques involves an experimental set-up which is both expensive and technically complex. Relatively few of these chambers exist and their usefulness in the present context is restricted to specific basic problems which do not require a natural free-living environment.