1. The aim of the present study was to evaluate the usefulness and reliability of a portable indirect calorimeter (Metavine; Vine, Tokyo, Japan). 2. We measured energy expenditure (EE) of elderly people (n = 191) at nursing homes using both Metavine and an authorized indirect calorimeter (Deltatrac Metabolic Monitor; Datex, Helsinki, Finland) and compared them. 3. Energy expenditure measured by Metavine significantly correlated with EE measured by the Deltatrac Metabolic Monitor (P < 0.001). 4. In particular, Metavine gave almost same results as the Deltatrac Metabolic Monitor, showing an excellent reliability, within the range of EE from 800 to 1500 kcal/day. However EE measured by Metavine below 800 kcal/day or above 1500 kcal/day required correction to agree with EE as measured by the Deltatrac Metabolic Monitor. 5. In conclusion, Metavine is a useful portable calorimeter for measuring EE in elderly people when used with sufficient recognition of its characteristics of data acquisition.