This is my response to a biochemistry assignment, in which our professor asked us to read and respond to the following article: https://www.medicalnewstoday.com/articles/287046
This is wild because just two days ago I bought a Lumen, which is a device that you breathe into throughout the day that claims to track your respiration exchange rate (RER), which is your CO2 to O2, exhalation/inhalation ratio. Lumen claims their device can train your metabolism by providing personalized advice on exercise and diet in response to your RER. This week’s assignment is a perfect opportunity to dig a little deeper into the relationship between RER and weight loss and see if this was a smart purchase.
Image from https://www.lumen.me/metabolic-flexibilityLinks to an external site.
The specific statement I would like to focus on from the article “Majority of weight loss occurs ‘via breathing’” is:
The results suggest that the lungs are the main excretory organ for weight loss, with the H20 produced by oxidation departing the body in urine, feces, breath and other bodily fluids.
This statement is derived from the works of Brown and Meerman, as published in their peer-reviewed article in the Britsh Medical Journal. The authors deduce that the equation for the oxidation of a single triglyceride is:
C55H104O6+78O2→55CO2+52H2O+energy
Triglyceride breakdown equation from Meerman and Brown, 2014.
Using stoichiometry, Brown and Meerman explain that 10 kg of fat requires 29 kg of oxygen which results in 11kg of H20 and 28 kg of CO2. Building on the 1949 research of Lifson et. al., which found that the synthesis of carbonic acid powers the exchange between oxygen in H20 and gaseous CO2, Meerman and Brown traced oxygen’s path and found that for every 4 O2's exhaled, 2 bind with hydrogens to form water. Therefore, according to Brown and Meerman, exhalation is indeed the main exit pathway for oxygens broken up by triglycerides, with the remainder exiting as H20, in a 2:1 ratio (Meerman & Brown, 2014).
These findings are reinforced by another peer-reviewed article that is essentially a lab directive for students to calculate oxygen and food intake against carbon dioxide output after exercise (Merritt, 2022). I found an interesting peer-reviewed paper on bats that found that the exhalation ratio in bats reflects the food type (protein, carbohydrates, fat) their muscles are currently burning (Youngsteadt, 2011). There are many articles that measure metabolic adaptation by way of carbon dioxide exhalation monitoring, such as the 2018 study by Moll et al., which found CO2 exhalation to be a reliable way to observe aerobic and anaerobic pathways in athletes, in addition to blood lactate concentration testing.
After my research, I am convinced that carbon dioxide exhalation is the exit pathway for catabolized triglycerides. However, I would like to see more articles that directly test this hypothesis.
Many questions remain. Can the Lumen breath analyzer show reliable readings that accurately reflect what the metabolism is burning? While metabolic flexibility (the ability to shift between fat burning to carbohydrate burning, for example) is affirmed by research (Goodpaster & Sparks, 2017), the Lumen itself is not proven to be a trustworthy measurement device (Hall, 2021).
Luckily, the Lumen has a money-back guarantee. I will test it out for myself and let you know my anecdotal experience!
REFERENCES
Meerman, R., & Brown, A. J. (2014, January 1). When somebody loses weight, where does the fat go? The BMJ. Retrieved November 22, 2022, from https://www.bmj.com/content/349/bmj.g7257Links to an external site.
Lifson, Nathan, et al. "The fate of utilized molecular oxygen and the source of the oxygen of respiratory carbon dioxide, studied with the aid of heavy oxygen." J Biol Chem 180.2 (1949): 803-11. https://web.archive.org/web/20171023163139id_/http://www.jbc.org/content/180/2/803.full.pdfLinks to an external site.
Merritt, Edward K. "Why is it so Hard to Lose Fat? because it has to Get Out through Your Nose! an Exercise Physiology Laboratory on Oxygen Consumption, Metabolism, and Weight Loss." Advances in Physiology Education, vol. 45, no. 3, 2021, pp. 599-606. https://go.exlibris.link/4sb7LsvF Links to an external site.
Youngsteadt, Elsa. "Bats Gorge during Exercise."American Scientist, vol. 99, no. 2, 2011, pp. 124. https://go.exlibris.link/W60561rX Links to an external site.
Moll, Kevin, et al. "Comparison of Metabolic Adaptations between Endurance‐ and sprint‐trained Athletes After an Exhaustive Exercise in Two Different Calf Muscles using a multi‐slice 31P‐MR Spectroscopic Sequence."NMR in Biomedicine, vol. 31, no. 4, 2018, pp. n/a. https://pubmed.ncbi.nlm.nih.gov/29393546/ Links to an external site.
Goodpaster, B. H., & Sparks, L. M. (2017, May 2). Metabolic Flexibility in Health and Disease. Cell Metabolism. Retrieved November 23, 2022, from https://www.cell.com/cell-metabolism/abstract/S1550-4131(17)30220-6Links to an external site.
Hall, H. (2021, July 27). Lumen’s Information Is Not So Illuminating. Science-Based Medicine. Retrieved November 23, 2022, from https://sciencebasedmedicine.org/lumens-information-is-not-so-illuminating/ Links to an external site.