Thirty-eight patients (13 men and 25 women) with impaired glucose tolerance, aged 33–70 yr, underwent a dietary program adding 20 g of raw bran to their usual diet without changing their dietary habits. After 1 mo of treatment, the areas under the curves for glucose and insulin were reduced from 26,214 ± 5618 to 24,529 ± 5207 g/min (P < 0.001) and from 15,893 ± 9714 to 12,440 ± 7377 mU/min (P < 0.001), respectively, cholesterol was reduced from 234 ± 40 to 212 ± 29 mg/dl (P < 0.001), and triglycerides were reduced from 108 ± 56 to 97 ± 50 mg/dl (P < 0.05). Body weight (initially 128.44% relative body weight) decrease 0.8% (P < 0.02). After the first month, 14 subjects were studied for a further 2 mo. Six patients continued bran feeding, and eight, who stopped bran, were used as controls. Patients who took bran maintained metabolic improvement over the 3-mo treatment period, while those who stopped bran did not.