Weight fluctuations in older adults linked to faster cognitive decline, study finds

Elderly people who experience fluctuations in weight or body composition may face a significantly faster decline in cognitive ability, according to new research.

The study, published in the journal Obesity, found that adults over the age of 65 who were underweight or whose weight shifted by more than five per cent were more likely to experience an accelerated deterioration in memory and thinking skills.

Researchers from the Department of Nutritional Sciences at Pennsylvania State University analysed 11 years of health data. “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,” said Muzi Na, associate professor of nutritional sciences and senior author of the study.

The team examined information from 4,303 participants in the US National Health and Aging Study between 2011 and 2021. Cognitive performance was measured using a composite index covering memory, orientation and executive function, while changes in body weight, body mass index (BMI) and waist circumference were tracked over time.

Findings showed that those who maintained a stable weight experienced the slowest decline in cognitive function. In contrast, individuals with the greatest weight fluctuations declined at a rate two to four times faster. Even relatively modest losses of five per cent were linked to poorer outcomes.

Weight cycling, the repeated loss and regain of at least five per cent of body weight, was associated with nearly double the decline compared with those whose weight remained steady. However, people who gained weight alone experienced a similar rate of decline to those who stayed stable.

Na cautioned against interpreting this as evidence that weight gain is beneficial. “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,” she said.

The researchers concluded that regular weight monitoring could be an important tool in protecting brain health. Na recommended self-monitoring as the most effective approach, advising people to weigh themselves at the same time each morning, for example, after waking, using the bathroom, and before breakfast, while wearing the same clothing.