Why We Gain Weight As We Age
A man swims in a pool - As we age, our muscles deteriorate, and they don't repair as quickly as they used to. But the good news is that exercise and weightlifting can still make muscles stronger. (Al Bello / Getty Images)
It's a pretty common lament, the idea that you just can't eat what you used to. But why is that so? And is it avoidable? There are a number of reasons why we put on the pounds as years go by, but take heart: There are ways to fight back — and win!
There are some particular biological changes that happen as we age. For one, aging muscles actually contribute to the increase in the amount of fat we store in our bodies, says Cheryl Phillips, president of the American Geriatrics Society.
"So, if you look at a woman who is 70 years old and compare her to what her body was like at 25 years of age, even though her weight may be exactly the same, she had more percentage of muscle in her body when she was 25 than she does when she's 70."
Our 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.
Building Strength At Any Age
And that's where exercise comes in. Wanagat says countless studies have shown that exercise — even among individuals in their 80s — works. It actually helps the muscle cells get bigger. And beyond size, it makes the muscles stronger.
"We aren't sure exactly how exercise makes muscles stronger, but we know that when we measure the grip strength of the hands or feet, grip is strongest just after exercise, even among people in their 80s and 90s. So weightlifting at any age offers low risk and great benefit, says Wanagat.
At UCLA, geriatrician and researcher Gail Greendale has just begun a second yoga study with seniors to try to figure out what poses work best for the older body. Greendale wants to understand how each yoga pose stresses muscles and joints. Then, she hopes to figure out how to modify the poses for the older body in order to maximize strength-building and minimize injury.
In addition, Greendale says that as we age the immune system can get out of whack, turning on an inflammatory response when there are no bacteria or viruses to kill, and keeping it on long after the body's invaders have left. Such an inappropriate inflammatory response can actually damage one's own cells in whatever part of the body the inflammation occurs, whether it's in muscles, joints or organs.
Ensuring such muscle and joint strength can also help fight this and other unfortunate aspects of aging, arthritis and inflammation. People over 75 are likely to have chronic joint problems, says Greendale. The joints are less able to tolerate the strain and stress of movement; they can be painful and swollen. Building joint and muscle strength can defend against that.
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PATTI NEIGHMOND: I'm Patti Neighmond. As we age, our appetites may not change, but that can mean weight gain. Just ask Shirley. We can't use her last name because of privacy issues at UCLA, where she's taking part in a study. But Shirley has something to say that might sound familiar.
SHIRLEY: Weight is a very hard thing to lose. It's easier to gain it than it is to lose it. And I'm - I probably have never been as heavy as I am now.
NEIGHMOND: At 73 years old, Shirley says she is overweight - which is why, when her doctor suggested she take part in a yoga study for seniors, she happily agreed. A few months later, she says, she saw big changes.
SHIRLEY: I had more endurance. I felt invigorated. When I left that class and I walked to my car, it was like the sun was shining and everything was terrific. So it made me feel very good.
NEIGHMOND: And she lost weight. Youve heard it all before: Exercise is even more important as we age because of the biological changes that happen to all of us.
Dr. Cheryl Phillips is president of the American Geriatrics Society.
Dr. CHERYL PHILLIPS (President, American Geriatrics Society): Muscle mass, the amount of muscle we have in our body, decreases with age. So, if you look at a woman who is 70 years old and compare her to what her body was like at 25 years of age, even though the weight may be exactly the same, she had more percentage of muscle in her body when she was 25 than she does when she's 70.
NEIGHMOND: When younger muscle cells get damaged, they're quickly repaired. That's not the case with older muscles, according to UCLA geriatrician Dr. Jonathan Wanagat.
Dr. JONATHAN WANAGAT (UCLA Researcher and Geriatrician): We don't know why muscles become smaller and weaker as we get older. There's a lot of different theories that have looked at this. I think one of the ones that's become increasingly interesting and popular is the idea that the stem cells within the muscle are not able to respond to damage or to aging the way that they did when we were younger.
NEIGHMOND: And if damaged muscle cells aren't repaired, they sort of whittle away and die, says Wanagat. So not only do we lose muscles cells as we age, the cells we're left with are sort of worn out.
Cheryl Phillips.
Dr. PHILLIPS: And if you think of muscles as being the energy powerhouse of our body, that's where most of the calories are burned. That's also - 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, and we know that energy as calories.
NEIGHMOND: And if you keep your caloric intake exactly the same, says Phillips, those unburned calories end up as fat. And that's where exercise comes in. UCLA's Wanagat says countless studies have shown exercise - even among individuals in their 80s - works.
Dr. WANAGAT: We know that exercise actually helps the muscle cells become bigger. And so there is an increase in the size of the muscles that happens with exercise, even in older individuals. But we also know that it makes the muscles stronger - sort of separately from that increase in size.
NEIGHMOND: At UCLA, geriatrician Dr. Gail Greendale has just started another yoga study with seniors, to try to figure out what yoga poses work best for the older body.
Dr. GREENDALE: What are the muscles and joint forces generated by each yoga pose, and will these muscle and joint forces be strong enough to be a training stimulus - that is to say, make people stronger.
NEIGHMOND: Without injury. Which is especially important due to another phenomenon of aging. Greendale says the immune system can get out of whack, turning on an inflammatory response when there's no bacteria or virus to kill, or keeping it on long after the body's invaders have left.
Dr. GREENDALE: An inflammatory cell is there to destroy another cell. So if it's on and there's no invader to destroy, it will damage your own cells. Wherever the inflammation is going on, it can actually damage the cells of that part of the body.
NEIGHMOND: Causing more problems to aging joints. Greendale's yoga study is getting under way now.
Patti Neighmond, NPR News.
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MONTAGNE: Youre listening to MORNING EDITION from NPR News. Transcript provided by NPR, Copyright National Public Radio.
