Stable Weight Tied to Cognitive Function as You Age

As we age, cognitive health becomes increasingly important. But could weight management be a factor in achieving this goal? A recent study in Alzheimer’s & Dementia found that the ability to maintain a stable weight may be a significant factor for brain health as you get older.

“Stability in BMI over time seemed to be protective, with a slower rate of cognitive decline, and that was true both in global cognition as well as specific cognitive functions,” says lead author Michal Schnaider Beeri, PhD, from the Icahn School of Medicine at Mount Sinai in New York City.

About the Study

Researchers looked at nearly 16,000 older adults who underwent dementia screening over a five-year period and found those with significant changes in BMI—representing a 5% increase or decrease—had a greater likelihood of cognitive decline.

This was true regardless of BMI status at the start, including normal weight or underweight categories. One reason that stable BMI may be protective is that the body is likely more able to maintain equilibrium with other important health markers like blood pressure and cholesterol, Dr. Beeri says.

“Previous research also indicates that BMI stability is associated with less frailty, disability, and early mortality,” she adds. “So there is clinical value in tracking BMI change, especially as we age, since it’s simple to measure.”

Mixed Evidence

Whether excess weight is harmful or helpful for brain health during aging is actually still up for debate, though. Dr. Beeri says she and other researchers have shown greater cognitive impairment and dementia with greater BMI in elderly participants in previous studies. For example, one study noted that waist circumference is correlated with poorer cognition in older women with Type 2 diabetes.

Another study following more than 450,000 people with obesity during a 12-year period beginning at midlife found an association between obesity and dementia for some age groups, but the risk diminished as people got older. In that research, people over age 80 with obesity actually had less risk of dementia than those in a non-obese control group.

“We and others showed more cognitive impairment and dementia with greater BMI in old age, but some have found no associations or even lower dementia risk in obese older adults,” says Dr. Beeri. “In addition, losing weight has also been associated with higher dementia risk.”

Movement Over Weight Loss

Given the recent study results, it is possible that rather than focusing on significant weight changes for better cognitive health and longer life, the emphasis as we age should lean more toward improving fitness and mobility. This may be true even with obesity.

That was the conclusion of a 2021 research review in the journal iScience, which looked at studies examining mortality risk reduction associated with weight loss, compared to physical activity. This review found the risk was lower with physical activity, according to study co-author Glenn Gaesser, PhD, in the college of health solutions at Arizona State University.

In fact, Dr. Gaesser suggests that people may benefit from a weight-neutral approach that focuses on fitness for health, rather than weight loss or weight management. When someone becomes more physically active, body weight may decrease, but in many cases does not change, he says. That can be frustrating for those who make weight loss into a primary goal.

“[A weight-neutral approach] eliminates weight loss from the equation when it comes to improving health,” he says.

Focusing on other aims like better mobility, improved function, and weight stability could help maintain motivation. Another important factor, he adds, is that it does not take much to see improvements in areas like blood sugar control and blood pressure.

“We have data showing that just 2 minutes of moderate-to-brisk walking every hour can improve blood sugar, for example,” he said.

Even just reducing the duration of sitting each day brings benefits. But Dr. Gaesser says a better option is making more moderate-to-vigorous-intensity exercise into a regular habit.