According to an account in the biography Trump Revealed by Michael Kranish and Marc Fisher, President Trump has rationalized his lack of physical exercise by saying he doesn’t want to deplete his body’s finite amount of energy. Here is the account provided in Kranish and Fisher’s biography:
After college, after Trump mostly gave up his personal athletic interests, he came to view time spent playing sports as time wasted. Trump believed the human body was like a battery, with a finite amount of energy, which exercise only depleted. So he didn’t work out. When he learned that John O’Donnell, one of his top casino executives, was training for an Ironman triathlon, he admonished him, “You are going to die young because of this.”
Trump’s view that human longevity is similar to a non-rechargeable battery is demonstrably false, but it brings up two separate claims that can be investigated scientifically: 1) Do humans have a finite amount of energy? and 2) Does exercising reduce a person's longevity?
Do Humans Have A Finite Amount of Energy?
The concept of some sort of overarching life-force or “energy,” while at odds with contemporary science, is a notion that puts Trump in the company of thinkers ranging from antiquity to the early 19th century.
One could argue that his battery metaphor blends neatly the Ancient Chinese concept of a life-sustaining energy known as qi with the medieval European concept of humors— a collection of four substances (black bile, yellow bile, phlegm, and blood) which were thought to be in balance when a person was healthy, but which in depletion were the cause of health problems and death.
From a more modern and scientific perspective, Trump’s “finite” amount of “energy” notion is reminiscent of the conclusions made by embryologists Jacques Loeb and J. H. Northrop, who in 1917 demonstrated a relationship between temperature and duration of life in fruit flies. These researchers used that result to argue that longevity was controlled by the presence or absence some unknown substance:
The observations [...] suggest that [the duration of life] is determined by the production of a substance leading to old age and natural death or by the destruction of a substance or substances which normally prevent old age and natural death.
While modern science increasingly supports the notion of an upper limit on human lifespan, it universally rejects the notion that a fixed amount of “vital energy” is the reason for such a limit.
During the course of the 20th century, scientists hunted for an elusive single factor limiting the human lifespan. They explored such possibilities as (for example) the cumulative effects of cells unable to replicate, as well as some sort of switch in gene expression later in life. These ideas ultimately gave way to the realization that multiple intertwined and complex systems collectively work to produce the upper limits on aging, as a 2003 review noted:
The search for a single cause of aging, such as a single gene or the decline of a key body system, has been replaced by the view of aging as an extremely complex, multifactorial process. Several processes may interact simultaneously and may operate at many levels of functional organization. Similarly, different theories of aging are not mutually exclusive and may adequately describe some or all features of the normal aging process alone or in combination with other theories.
So while a majority of scientists may be open to the idea of a biologically determined limit to human longevity (a finite amount of life, if you will), they would argue it is defined by the accumulation of multiple effects which make it increasingly improbable to survive past a certain age. Few, if any, would argue that this limit comes from an finite, internal “energy” that has “run out,” however.
Does Exercising Reduce a Person's Longevity?
This too, may seem like a question too obvious to even research, but it wasn’t actually until the 1900s that there was hard scientific evidence to suggest a link between longevity and exercise. A landmark 1953 study compared the occurrence of coronary heart disease across occupations of differing levels of physical rigor and found that, counter to Trump’s claims, more physically active professions lived longer lives as a whole:
The results show that the total incidence of coronary heart-disease is lower in the postmen than in the sedentary grades. Their case-fatality is also lower—a third in the postmen, compared with almost a half in the telephonists, executives, and clerks. Again, therefore, as with the transport workers, the early mortality of the physically active group is substantially less than that of the physically inactive.
The finding that physically active people tend to live longer is well accepted in the medical community. A 2015 study that included over 600,000 cases concluded that there is both a clear increase in longevity from physical activity, and that it takes an extraordinary amount of exercise to have any negative effect:
We observed this benefit threshold around 3–5 times the recommended leisure-time physical activity minimum, and no excess risk at 10+ times the recommended minimum. These findings are informative for individuals at both ends of the physical activity spectrum: they provide important evidence to inactive individuals by showing that modest amounts of activity provide substantial benefit for postponing mortality, while at the same time reassuring very active individuals of no exercise-associated increase in mortality risk.
There are various possible mechanisms for how exercise fits into the complex melange of factors that contribute to aging, but no mainstream theory is based on the depletion of a finite resource:
Exercise can help “add years to life”, and above all, “add life to years”, by partially counteracting the effects of aging on physiological functions and preserving functional reserve in elderly. Numerous studies have shown that maintaining a minimal quantity and quality of exercise decreases the risk of cardiovascular mortality, prevents the development of some cancers, lowers the risk of osteoporosis and increases longevity.
Because there is no quantifiable finite amount of energy that determines a person’s lifespan, and because numerous studies have shown that exercise increases longevity in humans, we rate this claim as false.