Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13C isotope ratio mass spectrometry.
OBJECTIVE
To determine dose-dependent relationship between ingested fat and its oxidation in the immediate post-prandial period in humans.


METHODS
Subjects were randomly selected for the study at the Dunn Clinical Nutrition Centre, Cambridge, UK. Subjects ingested naturally enriched 13C corn-oil doses (range 20-140g) in a whole-body indirect calorimeter, and were studied for 8 h. Ingested fat oxidation was estimated from the subject's breath 13C enrichment and total carbon dioxide production. Total fat and carbohydrate oxidation were estimated from non-protein oxygen and carbon dioxide exchanges. Endogenous fat oxidation was estimated as the difference between total fat and ingested fat oxidation.


RESULTS
The amount of fat dose oxidized was nonlinearly related to the amount ingested. On average, 25.6+/-2.7% of the mean fat dose was oxidized. A significant (r = - 0.72, P < 0.001) inverse correlation was found between the amount of fat dose and the proportion oxidized. Endogenous carbohydrate oxidation was negatively and significantly correlated to fat dose oxidized (r= -0.61, P < 0.01), but it was not correlated to endogenous fat oxidation.


CONCLUSIONS
There was a nonlinear relationship between amount of fat dose and its quantity that was oxidized in the immediate post-prandial period. The inverse relationship between the size of the fat load and the proportion that was oxidized post-prandially implies increased dietary fat storage beyond about 50 g in a normal resting adult. This has important implications for 13CO2-based studies.
Sonko
B J
BJ
University of Colorado Health Sciences Center, Department of Pediatrics, Denver 80262, USA. Bakary.Sonko@UCHSC.edu
Prentice
A M
AM
Coward
W A
WA
Murgatroyd
P R
PR
Goldberg
G R
GR
D000293:Adolescent; D000328:Adult; D001944:Breath Tests; D002153:Calorimetry, Indirect / Q000379:methods; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D003314:Corn Oil / Q000008:administration & dosage*; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D007700:Kinetics; D050356:Lipid Metabolism; D008066:Lipolysis; D008297:Male; D017711:Nonlinear Dynamics; D010084:Oxidation-Reduction; D019518:Postprandial Period; D013997:Time Factors
D002247:Carbon Isotopes; D004041:Dietary Fats; D002245:Carbon Dioxide; D003314:Corn Oil