The human body, even at rest, needs energy to perform necessary physiological functions. Strict conditions are required for measuring basal metabolic rate (BMR). Many factors that have a direct impact on BMR including the condition of autonomic nervous. All living systems are affected by external and internal environments. One factor in the external environment is the Earth's magnetic field, which fluctuates over a wide frequency range. A series of studies indicate that low frequency magnetic fields can affect cellular mitochondrial activity and impacts every cell's metabolism. Information on gas metabolism during respiration was obtained by indirect calorimetry using a system where the gas flow was continuously analyzed. Time varying local Earth magnetic field data were recorded at a magnetometer site located in Lithuania using 2 induction coil magnetometers. For all magnetic field data, power spectral density PSD was calculated for every hour (fast Fourier transformation) in the band between 0.32 to 36 Hz. Investigations of metabolic rate were performed in Lithuanian during 2016-2020 years. We assessed 395 persons: 116 men and 279 women. Conclusions: 1) Oxygen consumption has significant negative correlation with local geomagnetic field activity; 2) Metabolic rate decreases with increases in local geomagnetic time varying field power; 3) Measured metabolic rate decreases with increase of local geomagnetic field power.