I think they are genetic outliers, but they are also outliers in the stresses they are putting on their body. They genuinely need ~12k calories per day (Hall and Phelps).
They are genetic outliers because are able to operate at a elite level, but if you would learn more about sport and nutrition then those diets wouldn't look so extreme. They are eating goal based diets, that's different diet then normal person could or should consume. Hall and Phelps diet is not one that very sustainable but Metcalf one is actually the quite similiar to longevity diets. As such statements about that they are just genetic freaks this a disservice to diets they are eating and what we can learn from that.
If they would 4k their bodies will start to adjust to those levels, would that be their top performance probably not. The human body is very adaptable to any kind of circumstance.
If they would 4k their bodies will start to adjust to those levels, would that be their top performance probably not. The human body is very adaptable to any kind of circumstance.