Evidence for adaptive diet-induced thermogenesis in man during intravenous nutrition with hypertonic glucose

This study was designed to investigate the thermogenic effect of intravenously administered nutrition with glucose (given a fixed nitrogen intake of 12.5 g daily as amino acids) as the principal source of energy. The protocol was designed so that each patient received their energy intake in five consecutive periods of 3 days with intakes ranging from 6650 to 17,100 kJ/day with increments or decrements of 2600 kJ. Thermogenesis from administered glucose was evident between levels of energy supply of 6650 kJ/day and 17,100 kJ/day. The progressive rise in oxygen consumption and carbon dioxide production accounted for a total of 31% of the additional glucose which was administered. The net rate of fat synthesis from glucose reached a maximum 147 g/day at an energy supply of 14,500 kJ/day. This study suggests that both fat synthesis and the associated obligatory thermogenesis is the main component of diet-induced thermogenesis in response to glucose intakes in excess of 150 kJ day-1 kg-1. If the energy cost of fat synthesis (fat associated obligatory thermogenesis) is taken to be 22% of the total energy of the increase in glucose supplied, then only 9% (31-22%) of the glucose can be accounted for by adaptive thermogenesis.