Document Detail

Rates of nutrient utilization in man measured by combined respiratory gas analysis and stable isotopic labelling: effect of food intake.
MedLine Citation:
PMID:  3610664     Owner:  NLM     Status:  MEDLINE    
Rates of oxygen consumption and carbon dioxide production have been measured in healthy adults during 4 h of fasting followed by 4 h of hourly small meals. Both rates rose to new steady values during feeding, and the respiratory quotient (RQ) increased from 0.792 to 0.924. The RQ was consistent in repeat studies on any individual (coefficient of variation: 2.5 per cent), and differences between individuals were significant in the fasted but not the fed state. Simultaneous measurements were made of the rate of protein oxidation by primed constant infusion of (1-13C)leucine for 8 h. Rates were calculated from the enrichment of plasma alpha-ketoisocaproate and the production of 13CO2 in the breath, taking account of the incomplete recovery of 13CO2 and the changes in baseline enrichment resulting from natural 13C in the food. Leucine oxidation increased by 87 per cent during the feeding period. Rates of nutrient utilization were calculated from respiratory gas exchange and rates of protein oxidation. These showed that fat was predominant in the fasted state, contributing 61 per cent of total energy expenditure, compared with 27 per cent for carbohydrate and 11 per cent for protein. On feeding there was a switch to carbohydrate as the main fuel (62 per cent), with smaller contributions from fat (20 per cent) and protein (18 per cent). During feeding total utilization of each nutrient exceeded its intake from the diet, indicating storage in the body. Dietary carbohydrate was stored without conversion to fat. It is concluded that this method is useful for studying the control of nutrient utilization by food intake.
P J Garlick; M A McNurlan; K C McHardy; A G Calder; E Milne; L M Fearns; J Broom
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Human nutrition. Clinical nutrition     Volume:  41     ISSN:  0263-8290     ISO Abbreviation:  Hum Nutr Clin Nutr     Publication Date:  1987 May 
Date Detail:
Created Date:  1987-08-28     Completed Date:  1987-08-28     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8207516     Medline TA:  Hum Nutr Clin Nutr     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  177-91     Citation Subset:  IM    
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MeSH Terms
Dietary Carbohydrates / metabolism
Dietary Fats / metabolism
Dietary Proteins / metabolism
Energy Metabolism*
Nutritional Physiological Phenomena*
Oxygen Consumption
Reg. No./Substance:
0/Dietary Carbohydrates; 0/Dietary Fats; 0/Dietary Proteins

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