As people grow older, it is common for memory and thinking skills to slowly become weaker over time.
Many older adults may notice that they sometimes forget names, lose track of conversations, or take longer to make decisions.
Scientists have long studied the many things that may affect brain health in old age, including exercise, sleep, social activity, diet, and body weight.
Now, a new study from researchers at Penn State has found that changes in body weight may also play an important role in how quickly mental abilities decline later in life.
The research was published in the journal Obesity. The scientists looked at health information collected over 11 years from more than 4,300 adults aged 65 and older who joined the National Health and Aging Trends Study in the United States.
This large project follows older adults over many years to better understand aging and health problems that affect older people.
The researchers did not only look at how much the participants weighed. They also studied body mass index, often called BMI, and waist size. At the same time, they regularly tested the participants’ memory, awareness, and decision-making skills. These tests helped researchers see how people’s mental abilities changed as they aged.
The study found a clear pattern. Older adults whose weight stayed relatively stable over the years usually showed slower decline in memory and thinking. However, people whose weight changed often from year to year tended to experience much faster decline in their cognitive abilities.
According to the researchers, the results stayed similar no matter which body measurement they examined.
Muzi Na, an associate professor of nutritional sciences at Penn State and senior author of the study, explained that the message from the data was very consistent. The more a person’s weight moved up and down over time, the faster their memory and thinking skills tended to worsen.
To better understand the effect, the researchers divided the participants into groups based on how much their weight changed during the 11 years. People whose weight remained steady showed the slowest mental decline. In contrast, people with the largest weight changes experienced two to four times more decline in cognitive abilities.
The researchers also looked closely at different types of weight change. They found that losing at least 5% of body weight was linked to faster decline in brain function. Older adults who repeatedly lost and regained at least 5% of their weight also showed faster decline in memory and thinking skills.
Interestingly, weight gain by itself appeared to have a similar rate of decline compared with people whose weight stayed stable.
Still, the researchers warned that this does not mean older adults should try to gain weight. Earlier studies have already shown that obesity during middle age can increase the risk of dementia later in life. Dementia is a serious condition that affects memory, thinking, and the ability to manage daily life.
Na explained that body weight in older adults can be complicated. As people age, they often lose muscle while gaining body fat.
This combination can sometimes make extra body weight appear less harmful in studies, even though it may not actually protect health. Because of this, the researchers do not suggest that older adults intentionally gain weight.
Instead, the findings suggest that sudden or repeated weight loss in old age could be an important warning sign. It may show that a person’s overall health or brain health is changing. Doctors and families should pay close attention if an older adult’s weight begins changing noticeably over time.
The researchers also shared practical advice for tracking weight more accurately. Weight measurements taken during doctor visits can sometimes be inconsistent because people may wear different clothes or shoes at each appointment.
Na suggested that older adults check their weight at home in a regular way. For example, they can weigh themselves at the same time every morning after using the bathroom and before eating breakfast while wearing similar clothing or pajamas. Doing this can provide more reliable information about real body changes.
If an older adult notices ongoing weight loss or large changes in weight, it is important to discuss it with a doctor. Weight changes may sometimes be linked to illness, stress, poor nutrition, or other hidden health problems. Monitoring these changes carefully could help doctors identify health issues earlier.
The study does not claim that keeping weight stable can completely stop memory decline or prevent dementia. Aging still naturally affects the brain. However, the findings suggest that maintaining a more stable weight may help slow down the process and support brain health for a longer time.
As scientists continue to study healthy aging, this research adds another important piece to the puzzle. Along with staying active, eating nutritious food, sleeping well, and maintaining social connections, paying attention to body weight may also help older adults protect their memory and thinking abilities as they age.
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