Limited data are available concerning resting metabolic expenditure (RME) in cancer patients and the effect of RME by varying glucose intake. This study describes the measurements on 21 patients with colorectal cancer while fasting and with incremental levels of standard TPN‐glucose system by central vein. Following an overnight fast, the measured mean ± SEM percent difference from the predicted RME for the male group was 4.13 ± 1.67% and the female group, 2.09 ± 2.09%. The overall mean percent difference of 2.95 ± 1.45 suggests that colorectal cancer does not cause an increase in energy expenditure. Hepatic metastases in 11 of the patients did not influence RME. The data from the 21 patients indicate a statistically significant increase in RME with TPN compared to postabsorptive states in females of 37%, in males 21.88%, and combined of 29.88%. Progressively greater increases in RME were seen when calories provided incrementally exceeded the basal RME. Carbohydrate loading in excess of the patient's calorie need, as indicated by the respiratory quotient (RQ) greater than 1.0, results in fat synthesis and other energy‐costing processes. The basal RME demonstrates that these cancer patients are not hypercatabolic, but do respond to high‐level force‐feeding with markedly increased metabolic expenditures.(Journal of Parenteral and Enteral Nutrition12:8–14, 1988)