|Whigham Grendell, Leah|
|BUTZ, DANIEL - University Of Wisconsin|
|JOHNSON, LUANN - University Of North Dakota|
|SCHOELLER, DALE - University Of Wisconsin|
|ABBOTT, DAVID - University Of Wisconsin|
|PORTER, WARREN - University Of Wisconsin|
|COOK, MARK - University Of Wisconsin|
Submitted to: International Journal of Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2013
Publication Date: 9/2/2014
Publication URL: http://handle.nal.usda.gov/10113/61407
Citation: Whigham Grendell, L.D., Butz, D.E., Johnson, L.K., Schoeller, D.A., Abbott, D.H., Porter, W.P., Cook, M.E. 2014. Breath carbon stable isotope ratios identify changes in energy balance and substrate utilization in humans. International Journal of Obesity. 38(9):1248-1250.
Interpretive Summary: The ability to rapidly detect changes in energy balance (if a person is eating more or fewer calories than their body needs to maintain weight) would provide a compelling biofeedback tool to help individuals to lose weight. In a pilot study, we tested whether we could detect such energy balance changes using naturally occurring shifts in breath carbon isotope levels. Isotopes are molecules of the same element (such as carbon) that contain equal numbers of protons but different numbers of neutrons in their nuclei. In our atmosphere, we have naturally occurring levels of carbon-12 (predominant form) and carbon-13. Our study showed that when people consumed a calorically-restricted diet (40% fewer calories than their body needed for weight maintenance), their breath carbon isotope ratio (carbon-13: carbon-12) became noticeably lower. When they over-consumed calories (50% excess), their breath carbon isotope ratio became noticeably higher within hours. Existing methods for monitoring caloric intake (e.g. body weight) do not respond this rapidly to excessive caloric intake. Although additional research is needed to determine specificity and repeatability, this method may provide a biomarker for changes in caloric intake which could lead to a tool used to provide rapid feedback to individuals attempting to maintain a negative energy balance for the purpose of weight loss.
Technical Abstract: Rapid detection of shifts in substrate utilization and energy balance would provide a compelling biofeedback tool to enable individuals to lose weight. In a pilot study, we tested whether the natural abundance of exhaled carbon stable isotope ratios (breath d13C values) 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 prior to and at 1 and 2 h after breakfast, lunch, and dinner. Exhaled breath d13C values were measured by cavity ring-down spectroscopy. Using repeated measures ANOVA followed by Dunnett’s contrasts, pre-breakfast breath values on days 2-6 were compared to day 1 and postprandial day 7 time points were compared to pre-breakfast day 7. Energy restriction diminished pre-breakfast breath d13C values by day 3 (P < 0.05). On day 7, increased energy intake was first detected immediately prior to dinner (-23.8 ± 0.6 vs. -21.9 ±0.7‰, P=0.002 [means ± SD]), and breath d13C values remained elevated at least 2h post-dinner. In conclusion, when shifting between negative and positive energy balance, breath d13C values showed anticipated isotopic changes. Although additional research is needed to determine specificity and repeatability, this method may provide a biomarker for marked changes in caloric intake.