Can fasting really rejuvenate your cells?
Animal studies show convincing signs of cellular rejuvenation through fasting, and the first studies in people point in the same direction.
Fasting triggers a cellular clean-up process that helps cells break down and recycle damaged components. Restricting calories activates this process in ageing stem cells, which appears to restore their ability to divide and renew tissue. In mice, a multi-day fasting-mimicking diet also caused organs to temporarily shrink, after which, when normal eating resumed, the number of stem and precursor cells measurably increased, a pattern seen across multiple tissues.
In mice that received one of these fasting periods every two months from middle age onwards, lifespan was longer, abdominal fat mass was lower, fewer cancers developed, and bone density was better preserved. In addition, the number of new nerve cells in the memory centre of old mice's brains increased. It also turned out that very different dietary adjustments (fewer calories, ketogenic, high-fat) all appear to have the same effect on stem cells: greater self-renewal. Exactly how this works, and whether it is always beneficial, is not yet clear.
In people, the evidence is more limited but not absent. One study showed that three consecutive fasting-mimicking cycles lowered measured biological age by an average of 2.5 years, linked to less insulin resistance and less liver fat, independently of weight loss. A small exploratory study confirmed improvements in several health markers without serious side effects. A note of caution about the larger study: the lead researcher has a financial interest in the company that supplies the diet, which puts the findings in perspective.
The researchers themselves explicitly state that large-scale studies in people are still needed to definitively demonstrate long-term effects on disease prevention. The human data are exploratory for now. If you want to try such a fasting protocol, it is wise to discuss it with your doctor first, especially if you take medication or have an underlying condition.
The evidence rests on several animal studies (mice and a short-lived fish) and two studies in people, one of which involves a financial interest on the part of the lead researcher. The animal results are consistent and biologically well explained, but do not automatically translate to people. The human studies are still relatively small and exploratory; the researchers themselves acknowledge that large-scale long-term studies in people are lacking.
Does chronic inflammation accelerate the ageing of your cells?
Chronic inflammation demonstrably accelerates cellular ageing through a negative spiral that is difficult to break. The best evidence-based approach to tackling that spiral is through lifestyle factors that dampen low-grade inflammation, such as sufficient exercise and a diet low in ultra-processed products.
Do my stem cells run out as I get older?
Stem cells gradually become depleted and function less well as we get older. How quickly this happens varies from person to person and is still very much an active area of research.
Can meditation do anything about ageing at the cellular level?
Meditation appears to activate an enzyme that protects chromosome caps from ageing, although the studies are still too small to draw firm conclusions. Meditation is in any case safe and has positive effects beyond cell biology, so the barrier to trying it is low.
Does the protein GDF11 rejuvenate old cells?
GDF11 rejuvenates certain tissues in mice, particularly the heart, but whether this works in humans has not yet been investigated. There is no basis for acting on this now.
Does fasting help your cells clean themselves up?
Some forms of fasting clearly set the self-cleaning process of cells in motion in people. A time-window eating schedule or a multi-day period of substantial calorie restriction has the most support for achieving this.
Does fasting reset your immune system?
Fasting lowers inflammatory markers and has measurable effects on the gut microbiome that appear to be beneficial for the immune system. For healthy people who want to address low-grade inflammation, time-restricted eating is a practical starting point.