Abstract: Objective To investigate the resting energy expenditure（REE） in aged patients with type 2 diabetes mellitus in order to provide the theoretical basis for individualized diet and body weight control. Methods One hundred and sixty male patients were enrolled.Their age,body height,body weight,and BMI were 60-93 years（range,77.44±9.0 years）,157-180cm（range,169.8±4.73cm）,50-102kg（range,70.78±9.39kg）,and 18.6-36.1kg/m²（24.5±2.91kg/m²）,respectively.The patients were divided into type 2 diabetes mellitus group（n=110） and non-diabetes group serving as a control group（n=50）.REE was assayed with a portable indirect calorimeter,MedGem,by dividing the BMI of diabetes patients into＜24kg/m²,24-27.9kg/m² and≥28kg/m²,and calculated following the prediction equation of Harris-Benedict. Results The actual measured REE value in aged male patients with diabetes was 4.2%,which was higher than that in non-diabetes group.Both the actual measured REE value and the predictive value increased with BMI in diabetes patients（P＜0.05）.The correlation coefficient of the actual measured REE value and the predictive value to the body weight was 0.294 and 0.908,respectively（P＜0.05）. Conclusion Energy consumption increases in those who cannot effectively control their blood sugar level.Portable MedGem indirect calorimeter is easy to apply and plays an important role in direction of individualized diet and in control of blood sugar level.