If you need another reason to visit the gym this winter, a new study of almost 1,200 healthy, middle-aged men and women found that those with more muscle mass tended to have younger brains than those with less muscle.
The findings, which were presented in Chicago this month at the annual meeting of the Radiological Society of North America, add to growing evidence that building and maintaining muscle mass as we age could be key to building and maintaining brain health, too.
The researchers also found that those with high levels of deep belly fat had older brains, raising questions about the potentially negative effects of some types of body fat on the brain and how important it may be to combine weight training with weight loss, if we would like our brains to stay youthful.
ADVERTISEMENT
– – –
Why exercise is good for brains
The idea that exercise is good for our brains is hardly new. Past studies in rodents have shown that after exercise, the animals’ brains teem with a neurochemical called brain-derived neurotrophic factor, or BDNF. Sometimes referred to as “Miracle-Gro for the brain,” BDNF helps spark the creation of new neurons. So it’s not surprising that after exercise, mouse and rat brains typically sprout two or three times as many new brain cells as the brains of sedentary animals. The exercising animals also ace rodent intelligence tests.
People who exercise also show large increases in BDNF in their bloodstreams afterward.
ADVERTISEMENT
Other studies have shown that as few as 25 minutes a week of walking, cycling, swimming or similar exercise can be strongly linked to greater brain volume in older people, while taking as few as 3,000 steps a day helps slow cognitive decline in people at high risk for Alzheimer’s disease.
But most of this research involved aerobic exercise and the brain effects of endurance. Fewer studies have looked at the role of muscle mass. Many questions also remain about the role of body fat on brain health, especially the deep, interior fat around our bellies known as visceral fat, which can increase inflammation throughout the body, including, potentially, in the brain.
– – –
Is your brain young or old?
ADVERTISEMENT
For the new study, scientists at Washington University School of Medicine in St. Louis and other institutions decided to look deep inside people’s body tissues and brains with magnetic resonance imaging.
They turned to existing whole-body scans of 1,164 healthy men and women in their 40s, 50s or early 60s. “To understand dementia risk, we’ve got to focus on midlife,” said Cyrus Raji, an associate professor of radiology and neurology at Washington University School of Medicine and the study’s senior author. It’s in middle age that we typically start to develop – or avoid – most of the common risk factors for later dementia, he said, making it a critical time period to study.
The scientists used artificial intelligence to analyze the scans and determine people’s total muscle mass and body fat. The body fat was characterized as either visceral or subcutaneous, a different type of fat found just beneath our skin.
The researchers figured out the apparent age of people’s brains using algorithms based on scans of tens of thousands of other brains. These provided benchmarks of typical brain structure and volume for someone of any age. People’s brains could either match the benchmarks for their chronological age, or look like those of people younger or older. Older-looking brains face heightened risks for early cognitive decline.
– – –
More muscle means younger brains
The researchers found that the amounts of people’s muscle mass and their visceral fat were both strongly linked to their apparent brain age, though in opposing ways.
“The larger the muscle bulk, the younger-looking the brain,” Raji said. “And the more visceral fat that was present, the older-looking the brain.” People whose ratio of visceral fat to muscle mass was especially high – meaning they had a relatively large level of visceral fat and low muscle mass – tended to have the oldest-looking brains. (Subcutaneous fat was not linked to brain age in any way.)
The study didn’t look at how muscle and fat affect brains, but both tissues release a variety of biochemicals that can travel to the brain and jump-start various processes there, Raji said. The substances from muscles tend to promote the creation and integration of brain cells and neuronal connections; those from visceral fat do the reverse.
On a practical level, the findings underscore that resistance exercise “is super important” for healthy brain aging, Raji said. Most of us begin losing muscle mass in middle age, but strength training can slow or even reverse that decline.
Shedding visceral fat is likewise a good idea for our brains, he said. Both aerobic and resistance exercise will target visceral fat. Using weight-loss drugs such as Wegovy and other GLP-1 drugs can also substantially reduce visceral fat. But many people taking the drugs will drop muscle mass, Raji said – unless they also lift weights.
The study has limitations. It hasn’t been published or peer-reviewed. Because it’s not an experiment, it also can’t show that more muscle and less belly fat cause brains to age more slowly – only that those conditions are all linked to each other.
But its findings are plausible and align with those of a growing number of other studies, said Fang Yu, director of the Roybal Center for Older Adults Living Alone with Cognitive Decline at Arizona State University in Phoenix. She studies exercise and aging but was not involved with the new study.
Essentially, the study’s message is simple, actionable and even rhymes: If you want a younger, healthier brain, Raji said, “strength train.”