In clinical practice, predictive equations provide valuable information about energy expenditure that is used in estimation of metabolic needs for different individuals; however, accuracy of these equations is questioned in the tropical countries. The aim of this study was to determine which predictive equation is similar to indirect calorimetry in estimation of resting metabolic rate in obese diabetic and obese non-diabetic subjects. A random sample of 40 obese diabetic patients (cases) and 40 obese non-diabetic subjects (controls), 35 to 50 years of age, were selected from patients attending Gabir Abu-Eliz centre in Khartoum- Sudan. The PowerLab 8/35 with a gas analyzer (AD Instruments, Castle Hill Australia) was used for measurement of VO2, VCO2 and RER for each participant. Resting metabolic rate was derived from these parameters using Weir’s formula.(1,2) Three predictive equations (Harris-Benedict (3), Mifflin (4) and Food and Agriculture Organization/ World Health Organization/ United Nations University (FAO/WHO/UNU) equations (5) were assessed for their accuracy in predicting resting metabolic rate for the two groups. Using Weir’s derivation, resting metabolic rate (“mean±SD” kcal/day) was significantly higher among diabetic patients “1480.7 ± 274.2” compared to non-diabetics “1362.4 ± 184.8”; P= 0.027. The three predictive equations showed insignificant difference between the two groups; P>0.05. Resting metabolic rate measured with indirect calorimetry was significantly different from that measured with Harris-Benedict or FAO/WHO/UNU equations, P<0.05; whereas difference from Mifflin equation was statistically insignificant, P= 0.164. Resting metabolic rate, whether calculated or predicted, was significantly higher among males compared to females; P< 0.05. It was concluded that Mifflin equation is more reliable than Harris-Benedict and FAO/WHO/UNU equations in estimating resting metabolic rate in obese diabetic patients. Predictive equations are unlikely to detect difference in resting metabolic rate between obese diabetic and obese non-diabetic subjects.