The Longevity Diet (TLD) promises that following its recommended low-protein pescetarian dietary protocol and regularly eating a very-low-calorie “fasting-mimicking diet” (FMD) for five-day periods will delay aging and prevent, manage, or even reverse the damaging effects of aging-related diseases, such as diabetes, heart disease, cancer, Alzheimer’s disease, and autoimmune or inflammatory conditions. This book is authored by Valter Longo, PhD, a biochemist who has over two decades of experience conducting longevity research in cells, yeast, rodents, and humans. TLD claims that the optimal diet for health and longevity is one that is low in sugar and protein and primarily plant-based, with animal foods limited to a few servings of fish each week. The book recommends its proprietary 5-day FMD program to further augment the health benefits of the baseline diet. The Longevity Diet program received high marks for healthfulness, as there is good evidence that a moderate-calorie diet that is high in whole plant-based foods, low in refined grains and sugars, and supplemented with fish promotes health, particularly relative to the average “Western” or industrialized diet. The recommendations to limit the number of total meals per day and restrict the number of hours spent eating each day may also improve health. However, the existing literature is less clearly supportive of the book’s claims that optimal health requires eliminating all animal products besides fish or strictly restricting total protein intake, and research on the long-term health benefits of the FMD is more limited than this book might lead the reader to believe. This limited the scientific accuracy score of TLD, though the book does tend use references accurately. As far as popular diet books, TLD offers a comprehensive and potentially promising approach to addressing a wide range of chronic, aging-related health concerns. Yet the restrictiveness and expense of the complete dietary protocol might make it difficult for some people to follow.
Book published in 2018
Published by Avery – Penguin Books
First Edition, Hardcover
Review posted February 13, 2019
Primary reviewer: Hilary Bethancourt
Peer reviewer: Seth Yoder
We live in an era in which a large and growing proportion of the population is overweight or obese; cardiovascular disease, diabetes, cancer, and dementia are among the leading causes of death worldwide; and a substantial proportion of the population suffers from some kind of autoimmune disease. Yet not everyone succumbs to a chronic degenerative disease as they age. In fact, some individuals make it past 100 years old (become “centenarians”) with a sharp mind and free of characteristics typically associated with the top lifestyle-related diseases that begin to kill many humans in middle adulthood. What are those long-lived individuals doing differently to avoid disease and premature death, and what lessons can they teach us about ways to live longer, healthier, disease-free lives?
TLD proposes that the answer to not only a longer lifespan but also a longer “healthspan” comes down primarily to what, how much, how often and when we eat. TLD boasts of its use of “five pillars” to support its recommendation for a dietary regimen that will allegedly help prevent and reverse aging-related diseases and extend healthy lifespan. These “five pillars” include basic research, clinical trials, epidemiological research, studies on the lifestyles of centenarians, and “studies of complex systems”. The Longevity Diet program combines a daily low-protein, low-sugar, mostly plant-based diet with periodic 5-day cycles of a specially-formulated, proprietary “fasting mimicking” diet (FMD) program. The plan also promotes regular exercise, a reduction in the number of meals eaten per day, and a limit on food intake to ≤12-hours/day. Readers are promised that following this protocol will help reduce abdominal fat and decrease their risk for diabetes, cardiovascular diseases, Alzheimer’s disease, and autoimmune diseases while potentially prolonging lifespan. However, the diet is advertised as being less restrictive and depriving than other low-fat diet plans or dietary regimens requiring continuous caloric deficits.
I chose to read this book because of a long-standing interested in the conflicting perspectives about the role of animal products in human health and a curiosity about the potential for periodic fasting to promote healthy aging and reduce disease. My own PhD dissertation was focused on debates regarding the health benefits or detriments of including animal products in the diet, and it involved research with a population that intermittently “fasts” from animal products. Hence, I was curious to learn what other scholars have to say about these topics. I have also seen multi-day fasting, intermittent fasting, and plant-based diets become popular topics in the mainstream media, so I thought it would be important to explore what research is available to support the anecdotes shared on popular blogs and podcasts.
This review explored the following three arguments of the book:
1) The optimal diet for preventing and managing aging-related diseases and promoting longevity is one that is primarily plant-based (with the exception of fish) and very low in sugar, protein, and saturated fat.
2) High protein intake is associated with aging, disease, and premature mortality.
3) A periodic (2-12 times/year) 5-day fasting-mimicking diet (FMD), especially when combined with the Longevity Diet, can extend healthy lifespan and prevent or even reverse chronic aging-related diseases.
Following observations that the populations in the Mediterranean region, Okinawans of Japan, and vegetarian/vegan segments of the population in the United States and Europe tend to have reduced prevalence and incidence of aging-related diseases, a great deal of research has focused on the potential of plant-based diets to prevent and reverse disease and reduce premature mortality. The overarching message from the existing body of literature suggests that reducing intake of added sugars and refined carbohydrates and consuming more whole plant-based foods, such as whole grains, legumes, nuts and seeds, and fruits and vegetables is generally beneficial. The evidence on the purported health detriments of consuming animal products, on the other hand, is more contentious and controversial (see further explanation of claim 1 below).
See Scoring for Scientific Accuracy
Random.org was used to first create a list of
ten random numbers between one and eleven (the number of chapters in the book).
For each chapter number in the list, the random number generator was then used
to randomly select a reference number. Some of the randomly selected references
were ones that were already discussed above. Overall, TLD scored
high on the reference accuracy, as most of the references supported the claims
with which they were associated.
See Scoring for Reference Accuracy
The main “condition” this book addresses is
aging – the deterioration of cellular, metabolic, and immunological functions
that occurs with the progression of chronological age and increases our risk
for cardiovascular and metabolic conditions, cancer, cognitive decline, and
autoimmune disorders. TLD argues that we can delay or reduce
the negative impacts of biological aging by practicing dietary and lifestyle
habits that support cellular repair and keep inflammation and “pro-aging”
growth factors in check. In particular, the elimination of most animal products
and animal-sources of saturated fat, the reductions in protein, and the regular
implementation of FMD are said to help prevent, delay, or even repair some of
the cellular damage that accompanies the passing of years.
See Scoring for Healthfulness
Most unusual claim
TLD argues that aging is programmed and that both aging and death occur for the good of the species (e.g., to avoid overcrowding and overexploitation of resources). It is suggested that experiments with yeast “showed that a selfish group of microorganisms – in this case baker’s yeast that had been genetically manipulated to invest in their own protection and live as long as possible – would eventually become extinct, whereas shorter-lived microorganisms willing to sacrifice themselves and die early would seed future generations. In other words, the genetic alterations that make the organism act selfishly and live longer decrease its chances of generating healthy offspring” (page 17). It is reasoned, therefore, that dying is an altruistic act – that we die “to benefit others” (page 18).
The theory of programmed aging unravels when you consider that, for most species, extrinsic factors (e.g., predation, infection, starvation, cold, etc.), and not intrinsic factors from aging, are the primary causes of death. Most species simply do not survive long enough to even experience aging, more accurately termed “senescence.” Hence, senescence has very little impact on the biological fitness of most species in their natural environment, severely limiting the degree to which the forces of natural selection could have selected for a so-called programmed aging trait. Moreover, rarely does the benefit of the overall group (and group selection) override the strength of individual-level selective forces. The very suggestion of this book that individuals can “cheat” the system and live longer is an example of how quickly the whole notion of “programmed” aging would fall apart. If the system can be cheated, there will always be “cheaters” who will game the system; within any group those cheaters will be represented in higher numbers in future generations, even if it means not doing as well as an entire group.
So then the question is: why do we still age/senesce and why aren’t we seeing selection for longer and longer lifespans? The short answer is: there really is not a strong enough biological fitness advantage to living indefinitely past the reproductive years for there to be selection for immortality. Every organism has a finite amount of energy to invest in 1) growth, 2) maintenance and repair, or 3) reproduction. Resources invested in one area cannot be invested in another. Thus, for most organisms, energy is invested in growth and repair only insofar as such investments benefit reproduction. Beyond a certain point, it is not biologically advantageous to invest in cellular repair, and DNA mutations can accumulate, leading to senescence.
As Tom Kirkwood, a renowned biologist who has written a great deal on this topic, puts it: “we are not programmed to die, merely insufficiently programmed to survive.” We might be able to circumvent some of the effects of senescence through interventions, such as caloric restriction or fasting, that help reduce some of the wear and tear on the body. But even calorically-restricted organisms eventually senesce and die, not because they’re programmed to die but because they succumb to extrinsic factors (e.g., they can become more susceptible to infection) or because there is a limit to the intrinsic capacity to repair cellular systems.
A note on the potential difficulty and expense of this diet
It is important to discuss difficulty, expense, and sustainability of any dietary regimen. TLD makes a number of statements (e.g., pages 56 and 169) suggesting that the Longevity Diet is not that restrictive and is easier than plant-based dietary protocols that severely restrict fat. These suggestions downplay the fact that, for many, the elimination of meat, dairy, eggs, refined grains, and added sugars may feel, at least initially, extremely restrictive and difficult. Moreover, protein tends to be the more satiating macronutrient; the tight restrictions in protein could lead to feelings of hunger, at least in the early stages of trying to adopt this diet. If hunger persists, it can be difficult to sustain such a diet long-term.
With regard to expense, the basic dietary plan (not including the FMD) could be executed relatively inexpensively – at least if people prepare food at home. Rice and beans are generally cheap. Nuts and seeds, while not necessarily cheap, do offer a good calorie per dollar ratio. Fish can be expensive, but fish is only recommended a few times per week, and there are no apparent restrictions against canned fish, which is generally cheaper. Vegetables are not always cheap, but there are no explicit restrictions on frozen vegetables, which are usually a more economical solution. Sadly, if eating out, it is often cheaper to get fast food than a healthy plant-based meal. But that is a political issue in the US and not an issue with this diet. The greatest expense of the overall Longevity Diet protocol is the incorporation of the proprietary FMD, which costs $249 per 5-day period; for many people, the idea of spending $50/day to eat less than half their normal calories could seem like a steep price.
On the other hand, the Longevity Diet could require more of a time commitment to prepare food from scratch and buy groceries, especially if people are used to purchasing ready-made meals. That’s not to say that there are not easy meals that could be prepared to fit this diet (salad greens with canned garbanzo beans and some olive oil is a pretty quick meal to fix). But it may take some time for people to get in a rhythm in which this diet does not require so much time in planning and preparing meals.
Another thought-provoking claim
TLD recommends “eating at the table with your ancestors” (page 196), which this book describes as eating foods that your grandparents and their grandparents would have regularly consumed and avoiding foods they would not have consumed. There may be some benefit to following this advice, though TLD acknowledges that we lack evidence that such advice will prevent disease or promote longevity (page 199). What is commendable about this recommendation is that it recognizes that diverse diets across human history may have shaped how different individuals respond to a given food. As TLD describes, even so-called “health foods” may not be “healthy” for everyone. At the same time, it is also important to acknowledge that humans are incredibly flexible and adaptable eaters, and just because someone does not have an ancestral history of eating a given food does not necessarily mean that they should avoid it. Moreover, it is also worth pointing out that following the advice to eat at the table of our ancestors would mean including at least small amounts of foods like meat and eggs and, for at least for some European and African populations, dairy. All of our ancestors have a very long history of being omnivores.
So, this is not necessarily wrong, unusual, or bad advice. It just may be too restrictive for the many people who have no adverse health effects from and enjoy combining foods from various continents and cuisines.
As far as popular diet books go, this one has some great advice. The average person would likely benefit from following the recommendations to consume more whole plant-based foods, restricting or eliminating refined grain products and sugars, limiting the number of meals consumed in a day and the number of daytime hours during which they are consumed, and even undergoing periodic bouts of a low-calorie, low-protein diet. For many, however, the comprehensive diet plan outlined in TLD may feel extremely restrictive, and it is not clear that an optimal, health- and longevity-promoting diet necessarily needs to be so restrictive. Specifically, the evidence does not provide consistent support that most animal products need to be omitted or that total protein needs to be tightly limited in the context of an otherwise moderate calorie, whole foods, plant-rich diet. In fact, trading out some of the toast, pasta, and dried fruit from the meal plans in TLD for some eggs, yogurt, or poultry could actually be a good choice.
There is some fascinating research discussed in this book; the animal experiments conducted with the FMD are particularly intriguing. Still, given the existing nuances, caveats, and contradictory evidence, the claims and promises about the longevity-extending potential of the Longevity Diet protocol may be overstated. At the time this book was written, there were only two studies (including one pilot study) that had tested the effects of the FMD on cardiometabolic health markers. These studies only lasted for three months, and the results were not as compelling as presented in the book when comparing the health changes observed in the intervention group to those observed in the group that did not receive the intervention.
Notwithstanding, this book offers a comprehensive approach to promoting and improving a variety of health measures and outcomes. This book speaks not just to the composition of the diet but also to the timing of food intake and the importance of physical activity. It draws on different sources of evidence, including cellular research, animal models, observational studies, and clinical trials, to support its recommendations. Readers are reminded that the dietary approaches recommended in the book have not been tested in large clinical trials and that the diet, especially the FMD protocol, should be attempted only after the consultation of one’s doctor, especially if facing existing health conditions or taking medications.
In summary, the Longevity Diet protocol combined with the periodic 5-day FMD has potential to improve health markers and health outcomes. It is not yet clear that the Longevity Diet would lead to greater health improvements than any other dietary regimens that similar restrict processed foods, refined grains, added sugars, and total calories and promote the increased consumption of whole plant-based foods, and time-restricted eating. It is not clear that a similar whole foods, plant-rich diet that includes a greater proportion of protein or incorporates moderate amounts of animal products would be detrimental or less healthful than the Longevity Diet. This diet could feel very restrictive and difficult for the average person to follow, and the cost of the FMD could be a major barrier for many to incorporating that piece of the protocol. Moreover, we have yet to learn if the long-term effects of the FMD in humans is everything it is promised to be. Nonetheless, there is no reason to discourage anyone from trying the Longevity Diet if they have the means and motivation to do so, and it may very well provide the health benefit and relief from common aging-related health conditions that many people reading this book might seek.