Weight Loss or Fluctuations Tied to Faster Cognitive Decline

Adults over 65 whose weight decreases or fluctuates by more than 5% may experience faster cognitive decline, according to researchers in the Department of Nutritional Sciences at Penn State. The team published their findings in the journal Obesity. 

“We examined 11 years of data related to weight, body mass index and waist circumference,” said Muzi Na, associate professor of nutritional sciences and senior author of the study. “We conducted three different types of analysis on how those measures compared to cognitive decline. 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.” 

The researchers analyzed data from 4,304 older adults who participated in the National Health and Aging Trends Study between 2011 and 2021. In addition to the body composition metrics, the data also included measurements of memory, orientation and executive function. Na and the team combined those data points into a composite measure of cognitive function for their analyses. Aside from a couple small adaptations due to the COVID-19 pandemic, these measures were collected annually across the 11 years of data used in the current study.

“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.”

Muzi Na, associate professor of nutritional sciences

“As people age, their cognitive ability tends to gradually decline,” Na said. “This is natural, and we saw that in this sample. But we also saw that people whose weight varied the most experienced more rapid cognitive declines.”

The researchers grouped participants based on how much their weight varied during the study. People whose weight varied the least demonstrated the lowest amount of cognitive decline, while people whose weight varied the most demonstrated between two and four times as much cognitive decline. This result also held true when the researchers compared variability in waist circumference and body mass index (BMI) to variability in cognitive decline.

In another analysis, the researchers found that both losing at least 5% of one’s weight and cycling between weight loss and gain of at least 5% of one’s weight were associated with faster cognitive decline. The results indicate the dangers of losing or fluctuating weight for older adults, Na said.

Older adults who gained weight demonstrated roughly the same level of cognitive decline as those whose weight remained stable. However, the researchers explained this does not suggest that gaining weight is a good idea for older adults.

“Mid-life obesity is a known risk factor for cognitive decline later in life, but there is an 'obesity paradox' associating late-life obesity with a healthier cognitive trajectory,” Na said. “Some studies have revealed a complex interplay between age-related muscle mass loss and fat gain in older adults, and our study does not suggest older adults should gain weight.”

The findings suggest that monitoring older adult weight could provide additional information that could be useful in protecting cognitive health, but, according to Na, individuals should not rely just on doctor visits to track weight.

“From one doctor’s appointment to the next, the way weight is measured may not be consistent,” Na said. “Perhaps you have your coat and shoes on one time, and the next time you are in light clothes and socks. To make sure you understand what is happening to their body and brain, older adults should track their weight at home in a more consistent way. For example, a person could weigh themselves around the same time in the morning after getting up, before breakfast and after a bathroom trip while wearing the same pajamas. This would provide them with very consistent data. Then, if their weight is not stable, they need to let their physicians know.”

Reference: Flores AC, Wennberg AM, Leung CW, Na M. Variability in body weight and body composition and cognitive trajectories in older adults in the United States. Obesity. 2025:oby.24309. doi: 10.1002/oby.24309

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