In liquid enteral formulations, high molecular weight soluble starches may be able to replace glucose and low molecular weight glucose polymers that have high glycemic indices. Male rats were fed either commercial cornstarch, dextrose, modified soluble potato (70-75% amylopectin) starch, or modified soluble amylomaize-7 (70% amylose) starch for 4 wk. Body weights did not differ among the groups. Food consumption was significantly higher in the two modified starch-fed groups than in the two control groups. Commercial cornstarch, dextrose, modified potato starch and modified amylomaize-7 starch were 100 +/- 0, 100 +/- 0, 69.0 +/- 1.0 and 91.5 +/- 0.8% digestible, respectively (n = 9, mean +/- SEM). The modified potato starch-fed group deposited the least fat, protein and energy. In both modified starch-fed groups, liver weights were significantly greater than in the two control groups. In food-deprived rats, serum free fatty acid concentrations in the modified potato starch-fed group were significantly higher than in the two control groups, and serum glucose concentrations were significantly higher in the two modified starch-fed groups than in the controls. The insulin to glucagon ratios were significantly lower in the modified potato starch-fed and amylomaize-7 starch-fed groups than in the dextrose-fed control group. Serum protein concentrations, measured after food deprivation, were significantly lower in the modified potato starch-fed group than in the other three groups. Gluconeogenesis from fermentation products might account for the high serum glucose concentrations in the two experimental groups. These data indicate that only the modified amylomaize-7 starch may be useful in the development of food products for liquid nutritional supplements because of the high digestibility and the low resultant insulin levels.

The calorigenic response to a high protein test meal was studied in women with a history of childhood onset obesity. Obese and nonobese individuals were fasted overnight and basal oxygen consumptions determined the following morning. A semisynthetic 823 kcal high protein test meal was ingested within a 1-hr period followed by hourly determinations of oxygen consumption and plasma levels of insulin, free fatty acids, triglycerides, glucose, amino acids, and urea nitrogen. Amino acid levels increased faster and to a higher plateau in the nonobese group, while insulin levels increased and eventually decreased in a similar fashion in both groups. No differences in basal metabolic rate were detected. The postprandial increment in oxygen consumption was significantly less among the obese subjects. Diminished calorigenesis after each meal would result in accumulation of extra calories provided that caloric consumption is not appropriately decreased. These data suggest that a physiological aberration of energy metabolism may contribute to the development of childhood onset obesity.

Lipogenesis and insulin sensitivity are evaluated in adipose tissue, liver, and diaphragm of ob/ob and non-ob/ob mice. In ob/ob mice, hepatic fatty acid synthesis from [U-14C]glucose is elevated by 4 wk of age, and adipose tissue fatty acid synthesis increases at approximately 7 wk. Hepatic activities in ob/ob mice of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), malate dehydrogenase (EC 1.1.1.40), and alpha-glycerophosphate dehydrogenase (EC 1.1.1.8) are dramatically increased by 7 wk of age. Diminished insulin-stimulated glycogen synthesis is first noted in the diaphragm of ob/ob mice at 7 wk of age. Insulin-stimulated glycogen synthesis in adipose tissue of ob/ob mice is impaired at 3 wk. At 7 wk, insulin-stimulated fatty acid synthesis in adipose tissue of ob/ob mice is markedly increased. Adipose tissue glyceride-glycerol synthesis continues to increase throughout development, whereas fatty acid synthesis decreases after 7 wk. The data suggest that alterations in lipid synthesis occur very early in the development of ob/ob mouse, prior to expression to overt obesity, at which time a major contribution to lipogenesis is made by the liver. The altered de novo lipogenesis does not precede the reported diminution in energy metabolism.

Consumption of pork with a high PUFA content resulted in a decrease in the subjects' total plasma and LDL cholesterol and shifted the fatty acid composition from SFAs to PUFAs in the plasma and erythrocytes. Modification of the fatty acid composition of animal foods will be a useful approach to lowering the saturated fat consumption of Americans.

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