Many people in the life extension community follow some kind of diet. Historically, caloric restriction (CR) has been the most popular and most discussed option. Other popular diets include the Mediterranean diet and the Paleolithic diet.  In one sense, comparing these diets is like comparing apples and pears. The emphasis of caloric restriction is on how much we eat (given adequate nutrition) and the other diets are more concerned with what we eat. People who follow certain diets may also have different aims. In the case of CR, life extension. In the case of the Mediterranean diet, preventing and delaying cardiovascular and neurodegenerative diseases. And many who adopt a low-carb diet are (initially) motivated by securing sustainable weight loss.

Assuming that diet plays some role in longevity and disease, it is rather obvious that cryonicists should take a strong interest in choosing the right diet. As it looks to me, there are a number of important considerations.

1. The most important aim of a diet for cryonicists should be to avoid, or delay, neurodegenerative diseases. Extending your life and ending up with advanced Alzheimer’s Disease is worse than dying young and being cryopreserved under circumstances that optimize preservation of personal identity.

2. The choice to follow a particular diet should work for your genotype. Admittedly, nutrigenetics is a very young field but there is a growing recognition that human evolution has not stopped since the start of agriculture and that different populations respond differently to certain diets. And even within these populations we should expect individuals to respond differently to diet.

3. A decision to follow a certain diet should be based on empirical evidence, not on intuition, abstract theories, or thought experiments. In the case of choosing diets, this  means identifying a diet that has shown a favorable ratio of good outcomes in experimental studies, and humans in particular.

Putting this all together, it seems to me that a low calorie diet remains the most defensible choice for most cryonicists because it has been studied longer, studied more extensively, and has the most robust favorable outcomes. CR also seems to stand out favorably in that there are relatively few studies that find detrimental outcomes and its benefits seem to embrace many species and populations. Another advantage of CR is that it can capture all the important goals that life extentionists seeks from a diet: longevity, weight loss and prevention (or delay) of neurodegenerative diseases.

It may be the case that many of the benefits of CR actually come from a reduction of carbohydrates. But one of the problems with a paleolithic diet is that it may be more beneficial for certain populations than others. As Gregory Cochran and Henry Harpending demonstrate in their seminal book The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, human evolution did not stop when hunter gatherers started agriculture, and some populations are more adapted to agricultural products (such as milk) than others. Another concern about the paleolithic diet is the controversy surrounding saturated fat. For life extentionists who carry one or two copies of the ApoE4 gene, a diet high in saturated fat may actually increase the probability of Alzheimer’s disease. Others dispute this and recommend a diet high in (saturated) fat to prevent dementia.  In light of this uncertainty, the most prudent course of action may be to incorporate the emerging evidence against carbohydrates into a CR diet without emphasizing saturated fat.

There is an ongoing debate whether the longevity benefits of CR will be as great in humans as in lower species but the evidence so far seems to be that there are at least benefits in terms of delaying the onset of age-associated diseases. Whether these benefits are conferred through a change in gene expression or because they reduce the amount of chemicals that can participate in pathological events is not clear, but our incomplete knowledge about the mechanisms involved should not deter anyone from following CR. As I currently see it, the role of ongoing research into nutrigenetics and other diets should be to further calibrate and refine a low calorie diet to optimize it for a specific individual and to further delay the onset of neurodegenerative diseases.

CR seems to come closer to being a universal diet than other diets but it may be contra-indicated for some people, such as certain athletes and extreme ectomorphs. There are also cases in the life extension community of people who pushed it too hard (or neglected good nutrition), offsetting all the gains from the diet, or even endangering their own health. A diet that does not make a person feel good, is generally not a diet that is good, let alone one that can be sustained over time.  The aim of a diet should not be to conform to an impersonal set of recommendations, but to monitor your own response and increase the chance for personal survival.

Hans Reichenbach’s The Rise of Scientific Philosophy is among the most accessible and illuminating statements of logical empiricism. Although the book can be read as an introduction to philosophy, the central message of the work is that most of what constitutes philosophy is either (outdated) pre-scientific speculation or incoherent reasoning.

One of the most powerful chapters in the book is  about evolution. Reichenbach starts by contrasting the inorganic world, which obeys the laws of physics, with the organic world, which is goal directed. But then he goes on to show that the semblance of design and purpose can be accounted for by an evolutionary explanation, and that all biological phenomena can be reduced to physical phenomena. We do not need two separate sciences to account for non-living and living phenomena and can have a unified science about matter. Anticipating synthetic biology, Reichenbach suggests that future science should be able to create life through purposeful manipulation of inorganic matter.  Then Reichenbach moves from the evolution of the microworld to the evolution of the universe and reviews how contemporary findings in physics and astronomy affect questions about the past and the future of the universe.

Throughout his discussion of the relationship of science and philosophy, Reichenbach presents a number of distinct logical positivist positions:

It has become a favorite argument of antiscientific philosophies that explanation must stop somewhere, that there remain unanswerable questions. But the questions so referred to are constructed by a misuse of words. Words meaningful in one combination may be meaningless in another. Could there be a father who never had a child? Everyone would ridicule a philosopher who regarded this question as a serious problem. The question of the cause of the first event, or of the cause of the universe as a whole, is not of a better type. The word “cause” denotes a relation between two things and is inapplicable if only one thing is concerned. The universe as a whole has no cause, since, by definition, there is no thing outside of it that could be its cause. Questions of this type are empty verbalisms rather than philosophical arguments.

At the end of the chapter, Reichenbach criticizes the widespread view that there are other means of establishing knowledge which can answer questions that science cannot:

The elimination of meaningless questions from philosophy is difficult because there exists a certain type of mentality that aspires to find unanswerable questions. The desire to prove that science is of a limited power, that its ultimate foundations depend on faith rather than on knowledge, is explainable in terms of psychology and education, but finds no support in logic. There are scientists who are proud of when their lectures on evolution conclude with a so-called proof that there remain questions unanswerable for the scientist. The testimony of such men is often invoked as evidence for the insufficiency of a scientific philosophy. Yet it proves merely that scientific training does not always equip the scientist with a backbone to withstand the appeal of a philosophy that calls for submission to faith. He who searches for truth must not appease his urge by giving himself up to the narcotic of belief. Science is its own master and recognizes no authority beyond its confines.

This passage raises the important question of whether the position of logical empiricism is self-applicable. The same issue has been encountered by critical rationalists. One “solution” to this challenge is to make critical rationalism coherent by holding all positions open to criticism, including critical rationalism itself. This approach, called “pancritical rationalism” or “comprehensive critical rationalism,” has been proposed by the philosopher William Warren Bartley in his book  The Retreat to Commitment. Bartley’s solution has been criticized for producing logical paradoxes and its vacuous nature. Hans Reichenbach response was to develop a distinct probabilistic account of knowledge to avoid some of the remaining “rationalist” tendencies in contemporary empiricism.

Logical positivism found itself in the peculiar situation of struggling with its own internal consistency while at the same time seeing many of its basic tenets reflected in contemporary scientific practice.  One of Hans Reichenbach’s projects was to develop a scientific account of philosophy to resolve this situation.