This Article Full Text Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Toubro, S. Articles by Astrup, A. Search for Related Content PubMed PubMed Citation Articles by Toubro, S. Articles by Astrup, A.

Twenty-Four-Hour Respiratory Quotient: The Role of Diet and Familial Resemblance¹

The Research Department of Human Nutrition (S.T., A.A.), The Royal Veterinary and Agricultural University; Danish Epidemiology Science Centre at the Institute of Preventive Medicine (T.I.A.S.), Copenhagen University Hospital; Department of Biostatistics (C.H.), University of Copenhagen; Department of Internal Medicine and Endocrinology (N.J.C.), Herlev Hospital, University of Copenhagen; Copenhagen, Denmark

Address correspondence and requests for reprints to: Associate Professor Søren Toubro, Research Department of Human Nutrition, The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark. E-mail: st{at}kvl.dk

Body weight and obesity show familial resemblance that could be the result of familial correlation of fat oxidation, low levels of which have been implicated in the etiology of weight gain and obesity. We studied the familial correlation of both 24-h respiratory quotient (RQ), an index of the ratio of fat to carbohydrate oxidation, and the possible influence of dietary macronutrient composition expressed by the food quotient (FQ), i.e. the theoretical RQ produced by the diet. We measured the habitual FQ of the 7 days diet by weighed food records, followed by measurement of 24-h RQ in respiration chambers in 71 healthy Caucasian siblings from 31 families.

After adjustment for age, gender, and 24-h energy balance, 24-h RQ correlated in families as indicated by an intraclass correlation coefficient (r_i) of 0.31 (P = 0.03). FQ, adjusted for age and gender, was also a familial trait for the two days immediately preceding diet (r_i = 0.32, P < 0.01). The familial effect on 24-h RQ, adjusted for age, gender, and 24-h energy balance, remained after adjustment for the FQ of the two days preceding diet (r_i = 0.27, P < 0.05) and was reduced but not abolished after further adjustment for fasting plasma insulin plus free fatty acids (r_i = 0.24, P < 0.09). By a correlation analysis aimed at separating familial and individual nonfamilial factors influencing both 24-h RQ and FQ, we found a great but insignificant familial (^F = 0.49, P < 0.18) and a somewhat lower, but significant individual nonfamilial correlation (^NF = 0.35, P < 0.03).

We conclude that substrate oxidation rates measured by RQ exhibit familial correlation after proper adjustment for confounders such as energy balance, gender, and age, and that this effect could not be fully explained by preceding diet composition, fasting plasma insulin, and free fatty acids. Further RQ and the habitual dietary composition shared familial and nonfamilial factors.

This article has been cited by other articles:

				M. Hansen, R. Morthorst, B. Larsson, A. Flyvbjerg, M. H. Rasmussen, H. Orskov, A. Astrup, M. Kjaer, and K. H. W. Lange Effects of 2 wk of GH administration on 24-h indirect calorimetry in young, healthy, lean men Am J Physiol Endocrinol Metab, December 1, 2005; 289(6): E1030 - E1038. [Abstract] [Full Text] [PDF]

				C. Bitz, S. Toubro, T. M. Larsen, H. Harder, K. L. Rennie, S. A. Jebb, and A. Astrup Increased 24-h Energy Expenditure in Type 2 Diabetes Diabetes Care, October 1, 2004; 27(10): 2416 - 2421. [Abstract] [Full Text] [PDF]

				J. H. Goedecke, A. S. C. Gibson, L. Grobler, M. Collins, T. D. Noakes, and E. V. Lambert Determinants of the variability in respiratory exchange ratio at rest and during exercise in trained athletes Am J Physiol Endocrinol Metab, December 1, 2000; 279(6): E1325 - E1334. [Abstract] [Full Text] [PDF]

				P. T. Katzmarzyk, T. Rankinen, L. Pérusse, O. Dériaz, A. Tremblay, I. Borecki, D. C. Rao, and C. Bouchard Linkage and Association of the Sodium Potassium-Adenosine Triphosphatase {alpha}2 and {beta}1 Genes with Respiratory Quotient and Resting Metabolic Rate in the Quebec Family Study J. Clin. Endocrinol. Metab., June 1, 1999; 84(6): 2093 - 2097. [Abstract] [Full Text]