Running slowly for long distances is not the epitome of top-health. In fact it reduces body fat (good) and muscle mass. Just take a look at any marathoner, compare it with short-distance runners.
This looks like "Paleo diet" for exercise. And similarly to it, some aspects make sense, but others don't.
"Prolonged and excessive aerobic exercise efforts such as
marathons, ultra-marathons, full-distance triathlons, and
very-long-distance bicycle rides are inconsistent with our
genetic heritage. The pattern of exercise for which we are
genetically adapted involves a diversity of activities
performed intermittently, at moderate intensities and
moderate durations. Even in highly trained individuals,
high-intensity, multi-hour endurance exercise effort is
associated with damage to the myocardial cells and
connective tissue."
edit: See Table 2 in particular for a list of hunter-gatherer activities and corresponding modern activities. Note only 1 or 2 out of 13 activities involves running.
We didn't evolve to live as long as we do today. We didn't evolve to eat what we'll have to eat to sustain a population of trillions. If we strive to be what we evolved for, we'll go backwards. We should strive to be what we want to be, what we can be.
Parent poster said in their comment that running marathons all day is not healthy:
> > Running slowly for long distances is not the epitome of top-health
"The prospective clinical trials that have been performed
assessing the health effects of various exercise regimens
and the observational data are generally supportive of the
health benefits conferred by a hunter-gatherer style of
fitness regimen. A growing body of data indicates that
many of the benefits of exercise accrue at relatively low
to moderate levels of exercise. Continuous higher-level
activity, such as jogging 32 km/week, was not found to be
statistically better than walking 19 km/week for reducing
features of the metabolic syndrome.">"These profound and far-reaching changes in genetic expression may explain why cardiovascular fitness and daily energy expenditure on physical activity are among the strongest correlates of longterm health and survival"
This assumes you want longterm health and survival.