We studied the possibility of fat emulsions being a major calorie source, and if possible, a new infusion protocol without glucose for diabetic patients undergoing surgery. High dosages of fat emulsions and amino acids (HFHA infusions) were investigated as a substitute for conventional glucose-based infusions for 7 days after surgery. Without insulin and glucose, blood glucose was kept within the normal range, in spite of the fact that patients were recovering from major surgeries. Blood triglyceride and fatty free acids (FFA) increased after the start of the HFHA infusions but remained within normal range. Liver function tests and nutritional states estimated by nitrogen balance or rapid turnover proteins were no different from those of the conventional glucose-based infusion, but the significance of the HFHA infusion lies in the fact that it was applied to patients in whom it was impossible to administer enough calories by using the conventional glucose-based infusion, even if insulin was used. This HFHA infusion, which enables easy blood glucose control, sufficient calorie supply without complications, and is also nutritionally equivalent to the conventional glucose-based infusion, can be a new nutritional option for postoperative patients with impaired glucose tolerance.