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Published January 2, 2019 | Supplemental Material
Journal Article Open

Field-deployable measurements of free-living individuals to determine energy balance: fuel substrate usage through δ^(13)C in breath CO_2 and diet through hair δ^(13)C and δ^(15)N values

Abstract

Carbon isotopes of breath CO_2 vary depending on diet and fuel substrate used. This study examined if exercise-induced δ^(13)C-CO_2 changes in substrate utilization were distinguishable from baseline δ^(13)C-CO_2 variations in a population with uncontrolled diet, and compared hair isotope values and food logs to develop an isotope model of diet. Study participants included nine women with diverse Body Mass Index (BMI), age, ancestry, exercise history, and diet. Breath samples were collected prior to and up to 12 h after a 5- or 10 K walk/run. Indirect calorimetry was measured with a smartphone-enabled mobile colorimetric device, and a field-deployable isotope analyzer measured breath δ^(13)C-CO_2 values. Diet was assessed by food logs and δ^(13)C, δ^(15)N of hair samples. Post-exercise δ^(13)C-CO_2 values increased by 0.54 ± 1.09‰ (1 sd, n = 9), implying enhanced carbohydrate burning, while early morning δ^(13)C-CO_2 values were lower than daily averages (p = 0.0043), indicating lipid burning during overnight fasting. Although diurnal δ^(13)C-CO_2 variation (1.90 ± 0.77‰) and participant baseline range (3.06‰) exceeded exercise-induced variation, temporal patterns distinguished exercise from dietary isotope effects. Hair δ13C and δ^(15)N values were consistent with a new dietary isotope model. Notwithstanding the small number of participants, this study introduces a novel combination of techniques to directly monitor energy balance in free-living individuals.

Additional Information

© 2018 Taylor & Francis. Received 04 Oct 2018, Accepted 26 Nov 2018, Published online: 02 Jan 2019. This study was funded by the ASU-Mayo Foundation Obesity Solutions program with support from the Virginia G. Piper Charitable Trust. This project was funded by a Seed Grant of this program. It has a child account number of ZBS 0036, with a Coeus award number of 025579-012. The grant contract accountant listed is Nicholas Petersen (480) 727-9458.

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August 19, 2023
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