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Is intermittent fasting anti-ageing?
‘Anti-ageing’ creams, vitamin pills and diets are all over the internet. But could it be the case that stopping to eat anything for periods of time – intermittent fasting – actually turns back the clock on ageing? We asked 4 experts in biology, anti-ageing and physiology, ‘Is intermittent fasting anti-ageing?’, here is what they said…
Is intermittent fasting anti-ageing?
What is intermittent fasting?
Intermittent fasting, or ‘IF’ for short, is a diet in which you eat at specific times so that you experience periods of fasting. The frequency and length of the fasting vary between diets.
There are many intermittent fasting diets available, such as alternate-day fasting, periodic fasting and daily time-restricted feeding. Dr Josh Mitteldorf says “There are different ways to implement intermittent fasting. Most common is time-restricted eating, in which people stop eating early in the evening and then have a late breakfast, or no breakfast at all. Some people eat one meal a day. Some people like to fast a few days a month.”
Dr Nick Ashton says “Intermittent fasting means different things to different people, but for the purposes of this answer it is taken to mean an extended period of time (16-48 h) during which little or no calories are consumed followed by a period of unrestricted feeding.”
What is the evidence that intermittent fasting slows down ageing?
IF research has been carried out in model animals and in humans. In the lab, several studies in fruit flies, nematodes (a type of worm) and mice have found that IF can increase longevity in these animals.
Dr Nick Ashton says “In studies involving rats and mice, this sort of approach [IF] has been shown to improve health (for example, reducing risk factors for diabetes and heart disease) and to increase lifespan. For example, when young rats were started on an alternate day fasting diet (food was available for 24 h out of each 48 h period) at weaning their life span was 80% longer than rats that had normal free access to food. Even when this started in middle age, the fasted rats lived up to 40% longer than the rats which had unrestricted access to food.”
Such laboratory studies have revealed that IF doesn’t just increase longevity in these animals, but also has other beneficial health effects. Dr Zac Wylde describes, “There are some interesting and encouraging findings in rodents and other model organisms suggesting that intermittent fasting (IF) can increase physiological function and slow disease processes.”
It is important to remember these effects of IF seen in animals such as rats might not be the same in humans. Dr Wylde says “IF and ageing research is still in its infancy with evidence in humans lacking. For example, some studies have even found little or no benefit to IF when compared to regular calorie restriction. Further studies are needed to clarify how IF influences primary markers of ageing in humans.”
Although in its infancy, IF research has been carried out on humans and found some positive beneficial health effects. Dr Josh Mitteldorf says “In human studies with older residents, mostly in nursing homes, intermittent fasting improves some markers of health and there are suggestions it can lower risk of cancer and heart disease.” IF has also been shown to be an effective weight loss approach, which can in turn lead to positive health effects.
Human anti-ageing research is difficult because study participants would have to maintain a strict IF diet for many years and the study would have to last a lifetime to see any differences in longevity. There are also many other factors that affect ageing which might make it difficult to interpret results. Dr Nick Ashton says “Some studies in humans have also shown that intermittent fasting can reduce the risk of developing diabetes and cardiovascular disease, as well as leading to weight loss in obese subjects. However; theses studies typically only lasted for 2-6 months. In order to notice an effect on ageing, the period of intermittent fasting would have to last for years, if not the whole of life. This would be difficult to study and, more importantly, it would be difficult to maintain.”
Dr Markus Schosserer concludes, “A large body of evidence from simple model organisms (worms and flies), as well as from mice suggests that intermittent fasting (IF) is indeed able to slow down certain aspects of aging. IF in humans was shown to provide metabolic benefits, but direct evidence that it directly influences aging in humans is still lacking.”
How could fasting affect ageing?
The biology by which IF affects ageing is not yet clear. Dr Zac Wylde says “IF has been shown to stimulate molecular pathways (i.e., mTOR) involved in the pathway that the drug rapamycin targets (this drug has been shown to extend lifespan in some animal models).”
Should I start intermittent fasting?
Although preliminary research suggests that there are some benefits to IF, there are also side effects. Dr Wylde says “Currently we know relatively little on how dietary approaches such as IF influence reproductive health or the ability of a female to become pregnant in humans. Whilst I think skipping a meal or two is particularly good, especially in this world where high calorie junk foods are at our fingertips, I would always suggest exercising caution when making large lifestyle changes. I personally also think that there is a growing tendency for people to become fixated and anxious around "clean eating" so try to be cognizant of how an IF regime may also impact your mental health.”
There are lots of factors to take into consideration when deciding whether to start intermittent fasting. Our Metafact review covers some of these topics in more detail. It’s a good idea to talk to your doctor before drastically changing your eating habits.
Intermittent fasting may be anti-ageing, but more research in humans is needed.
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