NUTRITIONAL INFLUENCES ON LIPOGENESIS AND THERMOGENESIS AFTER A CARBOHYDRATE MEAL

In vivo lipogenesis and thermogenesis were studied for 24 h after ingestion of 500 g of carbohydrate (CHO) in subjects who had consumed either a high-fat, a mixed, or a high-CHO diet during the 3-6 days preceding the test. CHO oxidation and conversion to fat was significantly less in the high-fat diet group (222 .+-. 5 g) than in the mixed (300 .+-. 13 g) or high-CHO diet (331 .+-. 7 g) groups, resulting in a greater glycogen storage in the high-fat (278 .+-. 6 g) than in the other 2 groups (197 .+-. 11 and 170 .+-. 2 g). Net lipogenesis occurred sooner and lasted longer in the high-CHO group, amounting to 0.8 .+-. 0.5, 3.4 .+-. 0.6 and 9 .+-. 1 g of lipid synthesized in the high-fat, mixed and high-CHO groups, respectively. The thermic effect of the CHO load was 5.2 .+-. 0.5% on the high-fat, 6.5 .+-. 0.4% on the mixed diet and 8.6 .+-. 0.4% on the high-CHO diet. Significant relationships were demonstrated between the postabsorptive nonprotein respiratory quotient and net lipogenesis after the CHO load (r = 0.82) and between net lipogenesis and the increase in energy expenditure (r = 0.71). Apparently, the antecedent diet influences the amount of net lipogenesis and the magnitude of thermogenesis after a large CHO test meal. Lipogenesis remains too limited even after such large CHO intakes to cause an increase in the body''s fat content.