Overweight dementia patients lived longer than normal-weight peers, US study finds

People who were overweight or obese when they were diagnosed with dementia went on to live longer than people of normal weight, according to a study by researchers at New York University and Columbia University published in the Journal of Alzheimer's Disease and announced by the universities on October 5, 2026. The team analysed United States survey data on 4,523 adults who were free of dementia when first assessed and were later diagnosed with it, over the 24 years from 1998 to 2022. Compared with normal weight, being overweight at diagnosis was linked to a 16% lower risk of death, class 1 obesity to a 27% lower risk and more severe obesity to a 22% lower risk. The authors said the finding does not mean people with dementia should try to gain weight.

In mid-life, extra weight is a well-known risk factor for heart disease, diabetes and, over the long run, dementia itself. Yet among people already living with dementia, this study points the other way: those carrying more weight at diagnosis survived longer. Researchers sometimes call this kind of reversal an "obesity paradox", and it has been reported before in older people with other chronic illnesses.

The authors offer possible reasons. People with more body weight may have larger energy stores or more muscle to draw on as the disease progresses, when eating often becomes difficult and weight loss is common. They also looked at whether statistical bias could explain the result, for example the possibility that heavier people with poor health die of other causes before dementia is ever diagnosed. They reported that these checks did not suggest bias was a major driver, though the exact reasons for the link remain unclear.

The practical message is about nutrition, not weight gain. Unplanned weight loss in a person with dementia is a warning sign that families and doctors already watch for. The study adds to the case for tracking weight at diagnosis and protecting food intake as the illness advances. Chang stressed that the study was not designed to test whether patients should try to become overweight or obese.

For Indian families, where most dementia care happens at home, the finding is a reminder to keep a close eye on meals, appetite and weight in an older relative after a diagnosis, and to raise any steady weight loss with a doctor.

Short-term: Doctors and carers may pay closer attention to weight and nutrition at the time of a dementia diagnosis, treating it as a signal about how the illness may progress.

Long-term: The result invites trials on whether nutrition support that prevents weight loss can extend healthy survival in dementia, a question this study could not answer.

Who is affected: People diagnosed with dementia, family carers, geriatric doctors, dietitians and researchers planning dementia care.

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