known, and has many independent functions, de-activating several different signals by tacking on a phosphate group. The cell’s energy cycle uses ATP, which yields energy and is recycled in its low-energy form, AMP. Accumulation of AMP occurs when energy stores are low, and this signals a reduction in PKA. The article makes a point that, though the benefits of long-term caloric restriction have been studied extensively, this kind of rejuvenation of the immune system has never been observed with CR alone. Much of the article is theoretical, connecting decline of the immune system to many of the medical issues associated with aging. Arthritis and even Alzheimer’s disease are rooted in auto-immune reactions. The steep rise in cancer with age is believed to be related to the immune system’s failure to detect cancer in its early stages and to eliminate pre-cancerous cells. It is to be hoped that rejuvenating the immune system might have broad anti-aging effects. Why does it work? Evidence for programmed aging In write-ups of this material, the failure of stem cells with age is described as “dysregulation”, and the reason the strategy works is attributed to a clearing out of damaged and ineffective immune cells from the blood, as they are converted by the body to food. Perhaps you have noticed that this makes little sense. Certainly Valter knows this better than anyone, given his history, but he has chosen not to fight the abstract battle about evolutionary theory, because he knows it would likely interfere with the credibility of his other, practical and life-saving work. The point is that if the fasting body is able to rejuvenate and multiply the bone marrow cells that are responsible for blood and immunity (hematopoietic stem cells), then it is obvious that the body could do this as well or better when it has plenty to eat. If it wanted to. The fact that hardship and deprivation can induce the body to rejuvenate implies that aging is a programmed choice. Even when it looks as though the cells are suffering damage over time, that damage is entirely avoidable (indeed, repairable), and it is only with chemical switches that the repair mechanisms are turned off as we age. In PKA and IGF-1, Longo has identified two of the signals that keep the repair mechanisms dialed down, and make our health deteriorate with age. Why is the body intent on killing itself? It is an adaptation for population regulation, a response to natural cycles of boom and bust in population size. When times are good, the population expands too fast. Aging is a way of slowing down the population boom. This is why we age more rapidly when there’s plenty to eat. In times of famine, there is already plenty of death, and the danger is the opposite – that the population might plunge to extinction. This is why aging backs off in the face of hunger. (Ideas in this paragraph are not yet standard evolutionary theory, but this is a theme that I have developed , and it isthe core of my contribution to publications in the field.) Fasting in Ancient Religious Traditions Though they are not controlled and not founded in a knowledge of biological mechanisms, traditional writings nevertheless embody experience of large numbers of people over a long period of time, and I look to them for ideas, for cautions and confirmations. Before writing this piece, I had the impression that fasting was recommended in many religious traditions, and I eagerly googled associations with the 3000-year-old of India. I was surprised to learn that fasting for more than a day is regarded as an extreme practice, and that Ayurvedic texts don’t provide prescriptions or recommendations for long-term fasts, but rather cautions against fasting, suggesting that fasting practice has been prevalent for a long, long time, and the ancient Ayurveda was already reacting against it. Frequent 12-24 hour fasts, however are recommended, even prescribed in the Ayurveda. Eating the main mealearly in the day is a practice that ancient traditions and modern medicine agree on. Avoiding food for several hours before bedtime is part of yogic practice. For Buddhist monks in the Theravada tradition, all eating is confined to the morning hours, implying a daily fast of 16 hours. Implications for the clinician, for you and me I find it remarkable, if no longer quite surprising, that in write-ups of the therapeutic effects of fasting, medical professionals and researchers focus on what we can learn that will help us produce a drug that mimics the benefits of fasting. Fasting is providing all the benefits with little or no downside (except temporary hunger, need for warmer clothing); but medical science is busy search for drugs that will probably target just some of the signals that fasting sends, and will probably have more serious side-effects than fasting. Longo says that the constellation of benefits from fasting “would be difficult to achieve with any pharmacological orother dietary intervention.” It is deep in the culture of today’s medicine that the patient is passive and it is the doctor who is the agent of healing. Medical professionals de-emphasize all that the patient can do with diet, exercise and life-style modifications to improve his own health, despite the proven power of these regimes. Part of the problem is in the conection to capitalism, which creates a focus on what can be healed profitably, ignoring remedies that cannot be sold. Fasting and weight loss It is my experience that I don’t lose weight from fasting, presumably because I eat more before and after a fast. Other people I know have reported similar experiences, and both ancient texts and modern medical advice agree that fasting is not an effective way to lose weight for most people. That doesn’t mean it won’t work for you, if you have experience to the contrary. an account of his own 20-day fast, embedded in a very readable account of some fasting history. for thosewithout a Harpers subscription. Personal experience I’m now in Day 3, and it seems long only psychologically. In my weekly Thursday fasts, I sometimes experience headaches (one week in 5 or 6), and that hasn’t happened. I have the luxury of no busy schedule, no deadlines. That’s a good thing, because productivity on fast days is not reliable. During fasts, I don’t have the focus to be able to write computer code, and writing is often slow. But often deep and creative thoughts are given to me during fasts. I can sit contentedly for long periods of time without feeling a need to accomplish anything, or even to get up. I tend to a shorter night’s sleep, but enjoy naps during the day. Once in my life I tried public speaking on a day I was fasting, and I won’t do that again. Words come out more slowly, trying the patience of the audience. (My one experience was speaking to the Caloric Restriction Society, and my audience understood and were patient.) How long is optimal? Iwrote to Valter yesterday, asking this question. Does he have evidence from people suggesting how long it takes for the immune reset? Is it different for people who start with a lot of fat on their bodies compared to people who have nothing in reserve? His answer was short and to the point: “3 days is optimal for mice. For humans 4-5 minimum, depending on what you are trying to achieve” You can already tell I have a lot of faith in Valter as a scientist, and it is easy for me to believe that, from his experience, he knows more than he is able to publish. So I’m deep into Day 4 as I finish writing this. I’m a little spacey and my rhythms are disrupted, but I’m not suffering or food-obsessed. I plan to start fruit or juice soon.
