A new study from Penn State suggests that older adults who lose weight or experience weight changes over time may face faster memory and thinking problems.
The research, published in the journal Obesity, looked at over a decade of data and found a strong connection between weight changes and brain health in people over 65.
The study was led by Muzi Na, a professor in the Department of Nutritional Sciences. Her team studied 11 years of information from more than 4,300 older adults in the United States.
The data came from the National Health and Aging Trends Study and included yearly measurements of weight, body mass index (BMI), waist size, memory, thinking skills, and orientation. Using this information, the researchers created an overall score to measure brain function for each participant.
According to Na, it’s normal for cognitive abilities—like memory and focus—to slowly get worse with age. However, this study found that people whose weight changed more from year to year had a much steeper decline in their cognitive abilities.
“Any way we looked at the data, the relationship was crystal clear — the more a person’s weight varied from year to year, the faster that person experienced cognitive decline,” Na explained.
To better understand the pattern, the team divided participants into groups based on how much their weight changed over the years. They found that those with the most stable weight experienced the slowest decline in brain function.
In contrast, people whose weight changed the most showed two to four times greater cognitive decline. This pattern also held true when they looked at BMI and waist size instead of just weight.
Another important finding was that losing more than 5% of body weight or having weight that went up and down repeatedly (also by 5% or more) were both linked to faster cognitive decline.
On the other hand, older adults who gained weight during the study had similar levels of brain decline as those whose weight stayed the same. But this doesn’t mean gaining weight is helpful.
“Being overweight in mid-life is a known risk for brain problems later,” Na said. “But in older adults, some studies have shown that people with higher body fat may actually have better brain health—this is sometimes called the ‘obesity paradox.’ It’s complicated, and we’re not saying older adults should try to gain weight.”
Instead, the researchers suggest that older adults and their caregivers pay close attention to weight changes over time, as this could be a sign of future cognitive problems. However, Na noted that relying only on occasional doctor visits may not be enough.
She recommends that people weigh themselves regularly at home to track their weight more accurately. The best time to weigh yourself is in the morning, after going to the bathroom and before eating, wearing the same light clothes each time.
If someone notices that their weight is going up and down a lot, or if they’re losing weight without trying, it’s important to talk to a doctor. These changes may not just affect the body—they could also be a warning sign about brain health.
The study is published in Obesity.
Copyright © 2025 Knowridge Science Report. All rights reserved.
