Why do we gain weight as we age? Don't just blame all the bad stuff we eat ... let's blame nature, too. Darn those aging muscles:
In large part, that's because we lose muscle cells as we age. When younger muscle cells get damaged, they're quickly repaired. That's not the case with older muscles, according to UCLA researcher and geriatrician Jonathan Wanagat. He says we don't know why muscles literally shrink as we age. But there are a number of theories.
"I think one of the ones that have become increasingly interesting and popular is the idea that the stem cells in the muscle are not able to respond to damage or to aging the way they did when we were younger," says Wanagat. And if damaged muscle cells aren't repaired, they sort of whittle away and die, he says. Decreases in growth hormone, testosterone and estrogen levels may also account for the loss of muscle fiber and the inability of tissue to replenish itself.
In addition, the muscle cells we're left with are sort of worn out, according to Phillips. "If you think of muscles as being the energy powerhouse of our body, that's where most of our calories are burned. And when we talk about metabolism, what we're really talking about is how efficiently those powerhouse cells — the muscle cells of our body — burn the energy we bring in."
Energy is delivered to the body in the form of calories. And if you keep your caloric intake exactly the same as you get older, says Phillips, those unburned calories end up as fat.
Its sort of a one-two punch, says Wanagat. The energy powerhouse cells in muscles get damaged with age. That damage accumulates over time and, on top of that, the body's ability to repair that damage also dwindles with aging.
Patti Neighmond of NPR has more: Link