The objectives of this study were to obtain values for resting metabolic rate in Italians in relation to parameters of body composition, and to compare them to predicted values using the FAO/WHO/UNU equation. We performed a cross-sectional observational study of 131 healthy subjects (46 males and 85 females) at the Human Nutrition Unit, University Tor Vergata, Rome. Body composition was determined by dual energy X-ray absorptiometry (DXA) and resting metabolic rate was calculated using their Weir formula. Resting metabolic rate was 1865 - 234 kcal/day in males and 1354 - 154 kcal/day in females. These values decreased slightly with age. The relationships with weight and age were stronger than that with lean mass from DXA as independent variables in multiple regression analysis. Mean resting metabolic rates predicted with FAO/WHO/UNU and Harris-Benedict formula were not significantly different from measured values except for the Harris-Benedict value for females (p < 0.01). Individual differences between measured and predicted values were notably high. The measured values were higher than those reported in the literature. The prediction of resting metabolic rate is more accurate with simple anthropometric parameters than with fat-free mass obtained by DXA. The individual error in the predicted values can be so high that for individual use a measured value is preferred over an estimated value.