76 HawkMtn w/Rangers
14 LHHT
15 Girard/Quebec/LostTurkey/Saylor/Tuscarora/BlackForest
16 Kennerdell/Cranberry-Otter/DollyS/WRim-NCT
17 BearR
18-19,22 AT NOBO 1562.2
22 Hadrian's Wall
23 Cotswold Way
Athletes sometimes use IV therapy for recovery and even for performance enhancement. So I would imagine that IV nutrients like those (vitamins, minerals, amino acids, hormones) plus some IV glucose and breathing supplemental oxygen would likely raise the caloric digestive and respiratory limits of the human machine - to some degree. But at what expense? What would the negative effects be of increase workload on heart, kidneys, liver, etc. As a species we physiologically evolved to be able to perform at levels that provided some advantage of being able to survive long enough to procreate and raise the next generation. Athletic endurance was only part of the equation of those that are our biological ancestors. We are a compromise of the physiological and all the other traits of the most successful breeders. Athletic endurance at some of the extreme levels people are taking it to is a pretty recent phenomena in human history.
enemy of unnecessary but innovative trail invention gadgetry
I've been restricting daily caloric load for more than 20 yrs as pre hike prep for similar motivations as SEAL and Ranger schooling. You learn to operate mentally and physically at a high level without the over consumption U.S. civies are accustomed. Same with sleep. This approach to backpacking assumes a decent level of fitness pre hike. It's not a hike yourself into LD hiking shape(psychologically, physically, emotionally, spiritually) approach. It fits into UL backpacking. Operating on a restricted daily caloric load correlates with less food wt. Consider this approach uses the restricted caloric load technique on soldiers already fit with little body fat to make up for energy making them fitter and able to withstand extremes of combat.
Here is a link to the research article itself. https://advances.sciencemag.org/content/5/6/eaaw0341
As I read it, what the scientists found basically is that if you expend energy in excess of 2.5 times your Rest Metabolic Rate then the deficit can't be made up from eating more food instead you lose body fat and muscle mass. So for soldiers undergoing intense training, restricting calories below 2.5 times their RMR really doesn't make them fitter. It just increases loss of body fat and muscle mass. It may psychologically prepare them for the hardships they may encounter.
If you don't stand for something, you will fall for anything.