Breath carbon stable isotope ratios identify changes in energy balance and substrate utilization in humans.
Rapid detection of shifts in substrate utilization and energy balance would provide a compelling biofeedback tool for individuals attempting weight loss. As a proof of concept, we tested whether the natural abundance of exhaled carbon stable isotope ratios (breath δ(13)C) reflects shifts between negative and positive energy balance. Volunteers (n=5) consumed a 40% energy-restricted diet for 6 days followed by 50% excess on day 7. Breath was sampled immediately before and 1 h and 2 h after breakfast, lunch and dinner. Exhaled breath δ(13)C values were measured by cavity ring-down spectroscopy. Using repeated measures analysis of variance (ANOVA) followed by Dunnett's contrasts, pre-breakfast breath values on days 2-6 were compared with day 1, and postprandial day 7 time points were compared with pre-breakfast day 7. Energy restriction diminished pre-breakfast breath δ(13)C by day 3 (P<0.05). On day 7, increased energy intake was first detected immediately before dinner (-23.8±0.6 vs -21.9±0.7‰, P=0.002 (means±s.d.)), and breath δ(13)C remained elevated at least 2 h post dinner. In conclusion, when shifting between negative and positive energy balance, breath δ(13)C showed anticipated isotopic changes. Although additional research is needed to determine specificity and repeatability, this method may provide a biomarker for marked increases in caloric intake.
USDA ARS Human Nutrition Research Center, Grand Forks, ND, USA and University of Wisconsin-Madison, Madison, WI, USA at time of work; Paso del Norte Institute for Healthy Living, El Paso, TX, USA at time of publication.
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Whigham
Department of Animal Sciences, University of Wisconsin-Madison, Madison, WI, USA.
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Butz
University of North Dakota, Grand Forks, ND, USA.
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Johnson
Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA.
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Schoeller
Department of Ob/Gyn and Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, WI, USA.
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Abbott
Department of Zoology, University of Wisconsin-Madison, Madison, WI, USA.
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Porter
Department of Animal Sciences, University of Wisconsin-Madison, Madison, WI, USA.
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Cook
D000328:Adult; D001944:Breath Tests; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism*; D002149:Energy Intake; D004734:Energy Metabolism; D005247:Feeding Behavior; D006801:Humans; D019518:Postprandial Period; D013057:Spectrum Analysis / Q000379:methods; D013997:Time Factors; D015431:Weight Loss
D002247:Carbon Isotopes; D002245:Carbon Dioxide