Extreme events reveal an alimentary limit on sustained maximal human energy expenditure

* Extreme events reveal an alimentary limit on sustained maximal human energy expenditure. "We compiled measurements of total energy expenditure (TEE) and basal metabolic rate (BMR) from human endurance events and added new data from adults running ~250 km/week for 20 weeks in a transcontinental race. For events lasting 0.5 to 250+ days, SusMS decreases curvilinearly with event duration, plateauing below 3× BMR. This relationship differs from that of shorter events (e.g., marathons). Incorporating data from overfeeding studies, we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR; greater expenditure requires drawing down the body’s energy stores. Transcontinental race data suggest that humans can partially reduce TEE during long events to extend endurance." https://www.science.org/doi/full/10.1126/sciadv.aaw0341

https://www.science.org/doi/10.1126/sciadv.aaw0341 "Incorporating data from overfeeding studies, we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR" A good book the topic is Herman Ponzer's "Burn" The main issue seems the surface area of the GI tract.

The key insight is that you can eat more, but your body will not consume it. https://www.science.org/doi/10.1126/sciadv.aaw0341 And nobody is saying you can't expend more energy for shorter times. It is just that you can't sustain it over long times because of our metabolic limits.