Lets make a simple, almost childish question:

I think we all agree that life is all about chemical reactions at the end. So lets make an effort forget everything for a moment and focus heartlessly only on the reactions part of the organism. Moreover, there is no reason to believe that these reactions are not arbitrary.

Chemical reactions and Aging.

If the phenotype of an organism is the sum of its chemical reactions, one thing is obvious. That these reactions become different as we age. However, we don’t know whether the initial reactions are programmed to change and lead to the latter ones, or the transition is a result of other events. In other words, is it possible to maintain the same composition of reactions for a long time, thus preventing changes in phenotype, thus preventing further aging?

Answer: In the case our reactions are programmed to change, then things are more complicated. However, in the case that the reactions can be maintained as they are, then it can happen. And below is a possible way to achieve it.

The most important thing is to prevent changes. This can be achieved by providing a certain amount, composition and pace of initial substrates to the reacting system in the form of food. We are only interested in maintaining the system unchanged. We don’t care about the composition of this system, as long as it remains unchanged. This means that any diet that repeats itself every day,( that is providing everyday the same nutrients, in the same manner without any deviations in the routine) can cause the maximum of phenotype preserving in an organism, providing that the diet is viable and supplies all essential elements for life.

Question: Is there any existing evidence that this theory can work in reality?

Answer: A possible evidence can be the fact that the long term maintenance of the same weight (which is achieved by relatively stable food habits) pose an anti-aging effect. On the contrary, frequent changes in body weight accelerate aging.

Additionaly, anyone that tries to lose weight with the help of a specific nutrition, knows that even if he is very compliant to the perfect diet, he must periodically eat something else so as to further make changes in his body, because the body gets used to the diet and resists to further loss. It seems that eating the same food both in quality and quantity tend to cause stabilization of our body’s composition.

Seems a bit unlikely.

There have been studies on diet and aging on model organisms like C.eleganseg

http://www.ncbi.nlm.nih.gov/pubmed/23352664

But it is intermittent fasting. The other way is to fast a little so as not to trigger sexual maturation. Puberty switches off some body maintenance functions, and they don't all get switched back on properly. hence sex causes death.

Longevity is not everything in life.

You will die worrying about it.

It's been suggested that one reason humans and similar animals age and die is that big, complex things like us will accumulate injuries and infections and probably die eventually anyway, so mutations which enable young adults to improve their reproduction rate will be selected for even if those mutations also lead to earlier death, for example by switching resources away from bodily repair and towards reproduction. That possible explanation for the aging process is discussed here. A suitable diet could presumably still improve health and delay death, even if our evolutionary programming makes death inevitable (until we start bioengineering).

From the link:

Wikipedia wrote:A gene can be expressed at various stages of life. Therefore, natural selection can support lethal and harmful alleles, if their expression occurs after reproduction. Senescence may be the product of such selection.[19][20][21] In addition, aging is believed to have evolved because of the increasingly smaller probability of an organism still being alive at older age, due to predation and accidents, both of which may be random and age-invariant. The antagonistic plietropy theory states that strategies which result in a higher reproductive rate at a young age, but shorter overall lifespan, result in a higher lifetime reproductive success and are therefore favoured by natural selection. In essence, aging is, therefore, the result of investing resources in reproduction, rather than maintenance of the body (the "Disposable Soma" theory[22]), in light of the fact that accidents, predation, and disease kill organisms regardless of how much energy is devoted to repair of the body. Various other theories of aging exist, and are not necessarily mutually exclusive.

What is this thing about living long?

Weird.