The Hayflick Limit Theory of Aging (so called after its discoverer Dr. Leonard Hayflick) suggests that the human cell is limited in the number of times it can divide. Part of this theory may be affected by cell waste accumulation (which is described in the Membrane Theory of Aging).
Working with Dr. Moorehead in 1961, Dr. Hayflick theorized that the human cells ability to divide is limited to approximately 50-times, after which they simply stop dividing (and hence die).
He showed that nutrition has an effect on cells, with overfed cells dividing much faster than underfed cells. As cells divide to help repair and regenerate themselves we may consider that the DNA & Genetic Theory of Aging may play a role here. Maybe each time a cell divides it loses some blue-print information. Eventually (after 50-odd times of division) there is simply not enough DNA information available to complete any sort of division?
We also know that calorie restriction in animals significantly increases their life-span. In essence less fed animals live longer. Is this because they are subject to less free radical activity (see the Free Radical Theory of Aging) and therefore less cellular damage? Or is it that insulin and glucose damage (see the Cross-Linking Theory of Aging and the Neuroendocrine Theory of Aging for details) is less prevalent in them than in overfed animals?
The Hayflick Limit indicates the need to slow down the rate of cell division if we want to live long lives. Cell division can be slowed down by diet and lifestyle etc., but it is also surmised that cell-division can be improved with many of the protocols of the other aging theories described herein.
The use of ribonucleic acids (RNAs, the building-blocks of DNA), improve cell repair processes, enhance cellular capabilities and increase the maximum number of cell divisions in animals and vitro tests.