Rapid changes in weight—both up and down—were linked to an increased risk of dementia in a 2019 study in BMJ Open. Obesity is known to raise the risk for heart disease, type 2 diabetes, and other related conditions that have been linked to dementia. But less is known about the effect of rapid weight change.
The study involved 67,219 men and women (ages 60 to 79). Researchers used the difference between their BMI (body mass index, which reflects weight relative to height) at baseline and at a health screening two years later to calculate the BMI change. After two years, the incidence of dementia was monitored for an average of 5.3 years.
People who underwent a rapid change in weight—an increase or decrease of at least 10 percent— over the initial two-year period had a 20 percent higher risk for dementia than others whose weight remained stable. Weight loss is common in people with chronic conditions such as heart disease and cancer that have been linked to dementia risk.
Whether these findings truly reflect a cause or result of the development of dementia will require further study. What is clearer is that maintaining a healthy weight, avoiding tobacco, and limiting alcohol consumption may help protect against dementia. Adding body fat may be linked to increases in inflammation and other changes that may harm brain tissue.