The average life of an adult adipocyte (fat cell) is 7 to 12 years. As we gain or lose weight, the number of fat cells doesn't change. Instead, they either grow or shrink in size. This is what makes dieting so difficult!
The process of fat transfer completely removes fat from unwanted areas, and moves it to areas that need volume enhancement. The long life of the fat cell then causes the fat to stay where it has been re-implanted, allowing for a longer lasting result.
Fat transfer provides the same end result as fillers and implants, in a more natural way. Studies have also shown the stem cell population found within fat can improve skin quality and elasticity, which help maintain a youthful appearance.
Spalding et al. Dynamics of fat cell turnover in humans. Nature 453, 783-787.
Kim et al. Antiwrinkle effect of adipose-derived stem cell: activation of dermal fibroblast by secretory factors. J Dermatol Sci. 2009 Feb;53(2):96-102.
Park et al. Adipose-derived stem cells and their secretory factors as a promising therapy for skin aging. Dermatol Surg. 2008 Oct;34(10):1323-6.