Can You Boost Your Metabolism?
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"Boosting your metabolism" is one of the most persistent concepts in popular nutrition — and one of the most lucrative. Every generation gets its version: Victorian reducing salons with electric jiggle belts, thyroid extract sold on early radio, rainbow diet pills prescribed by actual physicians in the 1950s, ephedra stacks that killed an MLB pitcher and got banned by the FDA in 2004, and today's breath-sensing wearables and TikTok "internal showers." The intervention changes. The underlying premise — that metabolism is both broken and hackable — stays exactly the same.
In this episode, Zoë and Kylee break down what metabolism actually is and how total daily energy expenditure works (your basal metabolic rate accounts for roughly 60–70% of everything you burn before you touch a weight), trace the history of human attempts to manipulate something we didn't understand, and work through the evidence on the interventions most commonly marketed to athletes: green tea, capsaicin, cold water exposure, intermittent fasting, low-carb and fat adaptation protocols, and consumer breath analyzers like the Lumen. Zoë tested the Lumen firsthand and has some thoughts. Kylee has some clinical observations about what happens when athletes follow the app's recommendations. Different thoughts. Same landing place.
There's also a full breakdown of what actually determines your BMR — including Pontzer et al.'s 2021 finding that metabolism declines by roughly 2% per decade from ages 20 to 60, a substantially smaller effect than the wellness industry would like you to believe — why menopause doesn't crash your metabolism overnight, what adaptive thermogenesis is and whether you can reverse it, and what the 2024 Prieto-Belver et al. study in Nutrients found about carbohydrate periodization in trained athletes. The short version: eat your carbs. The long version is the episode.
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2. Hursel, R., Viechtbauer, W., Dulloo, A. G., Tremblay, A., Tappy, L., Rumpler, W., & Westerterp-Plantenga, M. S. (2011). The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta-analysis. Obesity Reviews, 12(7), e573–e581. https://doi.org/10.1111/j.1467-789X.2011.00862.x
3. Lowe, D. A., Wu, N., Rohdin-Bibby, L., Moore, A. H., Kelly, N., Liu, Y. E., ... & Weiss, E. J. (2020). Effects of time-restricted eating on weight loss and other metabolic parameters in women and men with overweight and obesity: the TREAT randomized clinical trial. JAMA Internal Medicine, 180(11), 1491–1499. https://doi.org/10.1001/jamainternmed.2020.4153
4. Prieto-Belver, C., Soriano-Maldonado, A., Marín-Cascales, E., & Herrero-Martín, G. (2024). Effects of a periodized carbohydrate diet on performance and substrate utilization in trained cyclists. Nutrients, 16(3). https://doi.org/10.3390/nu16030000
5. Zheng, J., Zheng, S., Feng, Q., Zhang, Q., & Xiao, X. (2017). Dietary capsaicin and its anti-obesity potency: from mechanism to clinical implications. Bioscience Reports, 37(3), BSR20170286. https://doi.org/10.1042/BSR20170286
6. Mountjoy, M., Sundgot-Borgen, J., Burke, L., Ackerman, K. E., Blauwet, C., Constantini, N., ... & Budgett, R. (2018). International Olympic Committee (IOC) consensus statement on relative energy deficiency in sport (RED-S): 2018 update. British Journal of Sports Medicine, 52(11), 687–697. https://doi.org/10.1136/bjsports-2018-099193
7. Burke, L. M., Ross, M. L., Garvican-Lewis, L. A., Welvaert, M., Heikura, I. A., Forbes, S. G., ... & Hawley, J. A. (2017). Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. Journal of Physiology, 595(9), 2785–2807. https://doi.org/10.1113/JP273230
8. Speakman, J. R., & Selman, C. (2003). Physical activity and resting metabolic rate. Proceedings of the Nutrition Society, 62(3), 621–634. https://doi.org/10.1079/PNS2003282