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The focus of most anti-aging research is to enable a person to live a long, healthy, productive life, but not to achieve immortality. However, there are many who actually want to increase their lifespan at least beyond the normal human maximum. There is only one known method that shows any promise of achieving this – calorie restriction. The problem with calorie restriction is that for it to be effective, a person has to eat so little that they may become very thin and even look as though they have an eating disorder, which is why usually only people who are very serious about anti-aging are interested in it.
The first scientific experiments on calorie restriction were done in the 1930s with mice. Since that time, studies have consistently found that by restricting the amount of food eaten by mice by 55 per cent from the age of one month, their average lifespan has increased from around 28 to 45 months (the human equivalent of from 78 to 125 years). There is a lesser effect at lower levels of restriction, although going over about 65 per cent leads to starvation, which obviously greatly shortens the lifespan. One month old for a mouse, however, is the equivalent of two years old for a human, so obviously calorie restriction cannot be started at this age in humans without affecting the growth of a child.
But what about calorie restriction begun at a later stage? A 44 per cent restriction in mice begun at the human equivalent of age 30 resulted in the average lifespan being extended from 78 to 90 years, while in another study a 27 per cent restriction starting at 40 in human years led to an increase from 78 to 100 years old. The same effects have been observed in many other animals, so it is likely that calorie restriction extends human life as well.
For any life extension effect to be observed with calorie restriction begun at an adult age, however, it needs to be phased in gradually, unlike a regime begun early in life. This has been found to be true in animal studies, and, if the life extension effects observed there apply to humans, then the necessity for a gradual introduction almost certainly applies to humans. The best guide is the way the person feels: a healthy calorie-restricted diet should make a person feel better, not worse. A human can typically only lose about a pound of weight per week safely; this translates to eating 500 calories per day less than what a person requires to keep a stable weight. For a person on an average diet, the eventual recommended restriction for humans is a reduction of 10 to 25 per cent of the normal caloric intake. The key is to not restrict the diet to the point where a person feels bad – when fat is broken down, toxins can be released, and an excessive release of toxins may obviously be very detrimental to a person’s health.
There are two complimentary theories as to why calorie restriction increases lifespan: a reduction in metabolism means less free radicals are produced, and, of course, because of the absence of obesity and its associated diseases. However, while an absence of obesity will certainly make a longer life more likely, it is not the weight reduction itself that causes an increased lifespan: eating more and burning the excess calories with exercise does not lead to an increased lifespan in animals, because it actually accelerates the production of free radicals. Exercise is of course still a healthy activity, with the extra free radical production offset by its other benefits, but from a life extension point of view it does not increase the maximum lifespan in animals at all. Calorie restriction is the only way to do it.
But the reality about calorie restriction, when practiced to the degree that has been observed to extend life in animals, is that very few people will either be able to prevent themselves from eating more than an effective regime allows, or will not consider the alleged benefits to be worth the side effects. Because the side effects can be severe: apart from loss of libido and feelings of irritability, the biggest downside is perhaps the opinion of friends and family, who often believe the person has developed an eating disorder or has a terminal illness. Nevertheless, some consider it all worthwhile if that’s what it takes to live longer.
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