Abstract 151

Background/Aim: The increasing incidence of obesity and NIDDM has lead to recommendations to reduce the dietary fat intake. As a consequence, to maintain energy balance, the CHO intake must be increased. This study was undertaken to determine if a high CHO/low fat diet adversely affected parameters of glucose metabolism in adolescents.

Subjects: Ten adolescents (6 boys, 4 girls) (14.5±0.4 y; 57±3 kg; Tanner IV-V) were studied in the overnight fasting condition on two occasions separated by 1 month and preceded by 7 days of diet containing either 60% CHO and 25% fat (HC) or 30% CHO and 55% fat (HF).

Methods: CHO and fat oxidation were measured over 24 h in a room calorimeter. [113C]glucose and 2H2O were used to determine glucose production rates (GPR) and gluconeogenesis (GNG), respectively. Differences were assessed by paired t-test.

Results: CHO and fat oxidation were (mean±SE) 52±3 and 31±3 %, respectively, on the HC diet and 34±2 and 51±2 % on the HF diet. Plasma glucose concentration was 4.8±0.1 (HC) and 4.9±0.1 (HF) mM; Insulin 8.2±0.9 (HC) and 6.3±0.7 (HF) µU/mL (p<0.05); C-peptide 1.7±0.2 (HC) and 1.5±0.2 (HF) ng/mL; GPR 12.8±0.5 (HC) and 12.0±0.4 (HF) µmol/kg min (p<0.01); GNG as a fraction of GPR 55±3 (HC) and 58±2 (HF) %.

Conclusion: Except for a slight decline in GPR and insulin concentration on the HF diet, other parameters of glucose metabolism were not affected by CHO intakes in the range of 30-60% of the dietary energy intake. Thus, at least in the short-term, healthy children adapt to extreme changes of the dietary CHO and fat intake by appropriately adjusting the substrate oxidation rates rather than glucose production and utilization.