“Aging gracefully” is a euphemism for getting old naturally: Gray hair, sagging skin, lost muscle tone, and sinking energy levels are what usually come to mind.
Source:Rejuvenation for Boomers: Restore Energy and Regain Your Youthful Glow

Here is an example of the other use for stem cells: to grow tissue that can be used to test and understand specific diseases. “Researchers are applying new stem cell technology to use skin samples to grow the brain cells thought to be responsible for the onset of Parkinson’s disease … [the] team will be [...]

A good example of what obesity does to your long term health: “Men who enter adult life obese face a life-long doubling of the risk of dying prematurely, new research has found. In a study presented today (Tuesday) at the International Congress on Obesity in Stockholm, researchers tracked more than 5,000 military conscripts starting at [...]