How Super-Athletes Use FAT for Fuel

In this episode, we discuss fat through the lens of performance and survival, and what happens when we push our energy systems to their limits. We also talk about how our bodies make adaptations via exercise to improve our ability to “burn” fat for fuel, and how our bodies conserve fuel during times of negative energy balance. Lastly, we preview the role of fat as an endocrine organ and the importance of its communication with the brain, as well as the critical role of exercise capacity for our future health.


00:00 – Introduction
01:49 – Extreme Endurance
02:54 – Fuel Source & Effort
03:12 – Glycogen
05:16 – Using Fat for Fuel
08:48 – Known Limits of Prolonged Energy Expenditure
10:21 – Metabolic Rate & Endurance Duration
14:00 – Physiology of Fat
16:18 – Insulin & Catecholamines in Fat Metabolism
19:10 – Fat as an Endocrine Organ
21:05 – Exercise & Maximal Fat Oxidation
22:02 – Exercise & Future Health
22:55 – Summary


  1.  Purdom, Troy, Len Kravitz, Karol Dokladny, and Christine Mermier. 2018. “Understanding the Factors That Effect Maximal Fat Oxidation.” Journal of the International Society of Sports Nutrition 15 (January): 3.
  2.  Loe, Henrik, Øivind Rognmo, Bengt Saltin, and Ulrik Wisløff. 2013. “Aerobic Capacity Reference Data in 3816 Healthy Men and Women 20-90 Years.” PloS One 8 (5): e64319.
  3.  Carey, Daniel G. 2009. “Quantifying Differences in the ‘Fat Burning’ Zone and the Aerobic Zone: Implications For Training.” Journal of Strength and Conditioning Research / National Strength & Conditioning Association 23 (7): 2090.
  4.  Arner, P., E. Kriegholm, P. Engfeldt, and J. Bolinder. 1990. “Adrenergic Regulation of Lipolysis in Situ at Rest and during Exercise.” The Journal of Clinical Investigation 85 (3): 893–98.
  5.  Sparks, Lauren M., Barbara Ukropcova, Jana Smith, Magdalena Pasarica, David Hymel, Hui Xie, George A. Bray, John M. Miles, and Steven R. Smith. 2009. “Relation of Adipose Tissue to Metabolic Flexibility.” Diabetes Research and Clinical Practice 83 (1): 32–43.
  6.  Maunder, Ed, Daniel J. Plews, Gareth A. Wallis, Matthew J. Brick, Warren B. Leigh, Wee-Leong Chang, Tom Stewart, Casey M. Watkins, and Andrew E. Kilding. 2022. “Peak Fat Oxidation Is Positively Associated with Vastus Lateralis CD36 Content, Fed-State Exercise Fat Oxidation, and Endurance Performance in Trained Males.” European Journal of Applied Physiology 122 (1): 93–102.
  7.  Thurber, Caitlin, Lara R. Dugas, Cara Ocobock, Bryce Carlson, John R. Speakman, and Herman Pontzer. 2019. “Extreme Events Reveal an Alimentary Limit on Sustained Maximal Human Energy Expenditure.” Science Advances 5 (6): eaaw0341.
  8.  Dunsworth, Holly M., Anna G. Warrener, Terrence Deacon, Peter T. Ellison, and Herman Pontzer. 2012. “Metabolic Hypothesis for Human Altriciality.” Proceedings of the National Academy of Sciences of the United States of America 109 (38): 15212–16.
  9.  Frandsen, J., F. J. Amaro-Gahete, A. Landgrebe, F. Dela, J. R. Ruiz, J. W. Helge, and S. Larsen. 2021. “The Influence of Age, Sex and Cardiorespiratory Fitness on Maximal Fat Oxidation Rate.” Applied Physiology Nutrition and Metabolism 46 (10): 1241–47.
  10.  Silvestris, Erica, Giovanni de Pergola, Raffaele Rosania, and Giuseppe Loverro. 2018. “Obesity as Disruptor of the Female Fertility.” Reproductive Biology and Endocrinology: RB&E 16 (1): 22.
  11.  Cohen, Paul, and Bruce M. Spiegelman. 2016. “Cell Biology of Fat Storage.” Molecular Biology of the Cell 27 (16): 2523–27.
  12.  Ravussin, Yann, Cuiying Xiao, Oksana Gavrilova, and Marc L. Reitman. 2014. “Effect of Intermittent Cold Exposure on Brown Fat Activation, Obesity, and Energy Homeostasis in Mice.” PloS One 9 (1): e85876.
  13.  Wang, Zhichao, Tinglu Ning, Anying Song, Jared Rutter, Qiong A. Wang, and Lei Jiang. 2020. “Chronic Cold Exposure Enhances Glucose Oxidation in Brown Adipose Tissue.” EMBO Reports 21 (11): e50085.
  14.  Brown, Aaron C. 2022. “Chapter 4 – Insights into the Adipose Stem Cell Niche in Health and Disease.” In Scientific Principles of Adipose Stem Cells, edited by Lauren Kokai, Kacey Marra, and J. Peter Rubin, 57–80. Academic Press.