The aim of science is not to open a door to endless wisdom, but to put a limit to endless error. —Bertold Brecht, The Life of Galileo
Except for man, all living things live with the environment. For instance, no matter which continent they are located, lions have never devised a novel way to obtain food in the jungle other than hunting down their prey and then fast 2-4 days before the next successful kill. To be clear, man is the smartest but not the strongest on the planet and certainly has no prayer, pound for pound, against a weight-matched chimpanzee as he would easily be mangled into several pieces within minutes. Despite man’s smartness with incredible ability to exploit the earthly resources, this has not come easily as it appears in modern times. Man is the only being whose survival and metabolic health are solely based on chronic exercise and, for sure, did not conquer the continents over several centuries by sitting in the tents with a full stomach.
The question is, for the purpose of public health, how much do we need to walk? As an African, I am familiar with repeating some words both in writing and everyday conversations to emphasize the essence of the statements we are trying to put forward while an English speaker would simply add an adjective. However, I would give you the liberty to determine how much walking you need realizing that a simple adjective failed an American author, in a book titled Burns, when he wrote: “To be Hadza is to walk. And walk. Every day”. In fairness, he did state that a hadza man and woman walk about 9 and 5 miles respectively every day. We have grown sophisticated and can fly across the continents within a few hours and I bet no one would care whether the cassava tubers for the garri they are eating in Lagos, Nigeria, were from Kogi or Benue State. The modern phrase about “business before pleasure” would equally apply to foraging before food in ancient times and still a reality in small traditional societies like the Hadzas.
This brings me to a well-done study on longevity and calorie restriction published in Science on February 10th, 2022 by Yale University researchers. If I may add, this was the first of its kind in humans, but unfortunately, they came to a wrong conclusion in terms of public health education. The researchers first tried to establish the baseline calorie intake of 200 participants and then asked some of them to reduce their calorie intake by 14% while the rest stayed on the same calorie intake. After 2 years, they analyzed how calorie restriction affected the thymus gland, an organ that produces “specialist infection- and cancer-fighting T cells”.
Typically, thymus ages quicker than the rest of the body and thus loses the ability to produce a new population of battle-ready immune cells called naive T cells as it gets smaller and invaded by fat cells in a process called involution. According to Dr. Vishwa Deep Dixit, the lead author of the study: “As we get older, we begin to feel the absence of new T cells because the ones we have left aren’t great at fighting new pathogens…that’s one of the reasons why elderly people are at greater risk for illness.” Interestingly, through magnetic resonance imaging, the researchers noted that the thymus glands of the participants on calorie-restricted were less fatty and got bigger in size but surprisingly found that those on the baseline calorie intake showed no change.
Furthermore, they noted changes in gene expression in adipose tissue or body fat of calorie-restricted participants because the immune cells (macrophages) resident in the body fat were blocked from producing a protein (PLA2G7) which activates inflammation. Therefore, their thymus glands were protected against inflammation and were able to produce more battle-ready T cells during the 2-year study. Here comes the wrong conclusion from the lead author: “These findings demonstrate that PLA2G7 is one of the drivers of the effects of calorie restriction (bold is mine).
For instance, it might be possible to manipulate PLA2G7 and get the benefits of calorie restriction without having to actually restrict calories, which can be harmful for some people.” How can calorie restriction be “harmful” to anybody when obviously the research was performed successfully for 2 years without reporting adverse events? Besides, having noted that PLA2G7 was “one of the drivers” of inflammation, if you try to block this protein via drug “manipulation”, the body will surely activate other pathways to stimulate inflammation without calorie restriction. This is why several medications are often needed to manage hypertension, diabetes, heart disease and other chronic diseases because there are multiple pathways leading to each of these diseases, and sooner or later some of the drugs would fail.
By the way, a 2018 article by Janet Lord and others showed that contracting muscles, even among active individuals above 70 years, protect thymus size by secreting a myokine called interleukin 15 and also ensure the survival of population of new naive T cells in the bloodstream by secreting another substance called interleukin 7. As noted by Mark Mattson, a fasting expert, in a 2014 article: “Medical school curricula place little or no emphasis on diet and exercise; instead, the focus is on specific diseases and the drugs or surgical treatments for those diseases.” Of course, any physician who thinks calorie restriction could be harmful to some people would hesitate to advise fasting in any condition.
Several studies have shown that the body responds defensively when subjected to normal metabolic stress through one or combination of physical activity, fasting or calorie restriction by increasing cell resistance to maintain health and fend off sickness. The result of this new study is self-evident: that calorie restriction sharpens the immune system against new pathogens and no new pill by Big Pharma is necessary. We just cannot medicate health by avoiding physical activity and eating all we want when we want just because they are available with zero physical exertions. No, we can’t eat our cake and then have it!
Mukaila Kareem, a doctor of physiotherapy and physical activity advocate, writes from the USA and can be reached through makkareem5@gmail.com
