SYNOPSIS: “ Worth All the Sweat ” (Economist, Jan. 2012); “ Exercise as Housecleaning for the Body ” (NYT); "Exercise as Housecleaning for the Body," Gretchen Reynolds, NYT, Feb. 2, 2012) We’ve all heard about the many downsides of being under pressure, but did you know that when it comes to the health of your cells, stress can be a good thing? Autophagy is the process by which cells clean out the “garbage” that accumulates in them. Cells constantly recycle old proteins and internal dead parts to use for energy. When the body undergoes stress—food deprivation or physical exertion—autophagy kicks in. This mechanism could help animals and humans survive through leaner times when sustenance is not readily available. Researchers have known for a while about the anti-aging effects of cell recycling. When animals are fed a near-starvation diet, they live longer. Some intrepid humans have adopted this practice with the hope of prolonging their lives. Recent...