Abstract: Objective To measure the resting energy expenditure（REE） in adults with different body weights using a portable MedGem hand-held indirect calorimeter and compare it with that measured following the Harrid-Benedict prediction equation. Methods A total of 601 healthy adults（426 males and 175 females） at the age of（48.85±8.21）years were enrolled in this study.Their body height,body weight and body mass index（BMI） were（169.2±7.23）cm,（72.8±10.9）kg and（25.37±2.93）kg/m²,respectively.The subjects were divided into BMI＜24kg/m² group,BMI（24-27.9）kg/m² group,and BMI≥28kg/m² group.Their REE was measured using a portable MedGem hand-held indirect calorimeter and their body compositions were analyzed following the Harrid-Benedict prediction equation. Results The REE measured with the portable MedGem hand-held indirect calorimeter was（6 788.37±812.55）kJ/d and（5 605.04±725.56）kJ/d in males and females,respectively,which was higher than that measured following the Harrid-Benedict prediction equation（10% vs 1.5%）.The REE increased with the increasing BMI.However,when the influence of fat free mass（FFM）on REE was excluded,the REE/FFM ratio was lower in males than in females.The difference in REE measured with the portable MedGem hand-held indirect calorimeter and following the Harrid-Benedict prediction equation increased with the increasing BMI.The average REE of 54.4% was an acceptable limit. Conclusion Portable MedGem hand-held indirect calorimeter is a simple and convenient device and can be used in providing parameters for individualized nutrition and control of body weight.