New research published in the Journal of Health Psychology suggests that a specific measurement of body shape called the Body Roundness Index provides evidence of a link between excess belly fat and depression in people with dementia. The findings indicate that older adults with dementia who have a more rounded body shape face significantly higher odds of experiencing depressive symptoms. This provides a potential new tool for doctors to identify and monitor mental health risks in older patients experiencing cognitive decline.
Scientists conducted this study to better understand how physical health conditions contribute to mood disorders in older adults experiencing cognitive decline. Felipe Kenji Sudo, a medical doctor and researcher affiliated with the D’Or Institute for Research and Education in Brazil, explained the motivation behind the project. “Depression is very common in people with dementia, but it is not always easy to recognize or anticipate in everyday clinical practice,” Sudo said.
“We wanted to explore whether simple measures related to body fat distribution might be associated with depression in this population,” Sudo noted. Dementia is a globally widespread condition characterized by severe memory and thinking problems. A significant portion of dementia cases tends to be associated with risk factors that can be modified or treated.
Among these preventable factors, carrying excess body weight has emerged as a major contributor to poor brain health. Excess body fat can lead to chronic, low-level inflammation throughout the body. This persistent inflammation tends to disrupt normal brain activity and can accelerate the deterioration of brain cells.
Such inflammation can also cause physical stress on the body and interfere with the way the brain handles hormones. These combined physical stressors often pave the way for depressive symptoms. Because obesity, depression, and memory loss share these underlying biological pathways, scientists wanted to see if measuring body fat could predict mood problems.
However, assessing body fat in older adults presents unique challenges. As people age, they naturally lose muscle and bone density. This means the traditional Body Mass Index, which calculates a score based on a person’s height and weight, might severely underestimate how much fat an older person is actually carrying.
To address these limitations, researchers have developed newer mathematical formulas that attempt to capture body fat distribution more accurately. One of these formulas is the Body Roundness Index, which uses a person’s height and waist measurements to conceptualize the body as an oval shape. Scientists designed this study to determine if these newer formulas could predict depression better than older methods.
To explore this relationship, the scientists analyzed data from 601 older adults living in the community. These participants ranged in age from 60 to 91 years old and were evaluated at a specialized memory clinic in Brazil between 2015 and 2024. All participants had completed at least eight years of formal education and underwent a standardized medical interview and physical examination.
During the physical examination, medical staff measured each participant’s height, weight, and waist size. The researchers then used these numbers to calculate multiple different estimates of body fat. These included traditional metrics like the Body Mass Index and simple waist circumference.
They also calculated several newer metrics designed to capture body shape, such as the Waist-to-Height Ratio, the Conicity Index, and the Body Roundness Index. The Conicity Index evaluates how much a person’s body resembles a double cone. Meanwhile, the Body Roundness Index assesses overall circularity.
A trained specialist evaluated the cognitive abilities of the participants using a variety of standardized tests. These tests measured memory, attention, language skills, and visual recognition. Based on these tests and reports of daily functioning, 239 of the participants were officially diagnosed with dementia.
The researchers also evaluated everyone’s mental health by assessing depressive symptoms using a specialized 15-item questionnaire designed specifically for older adults. Participants scoring a five or higher on this scale were classified as having depression. The scientists also measured anxiety levels to ensure they could separate the effects of anxiety from actual depression.
When looking at the entire group of 601 participants, the researchers found no relationship between any of the body fat measurements and the presence of depression. However, the data revealed a very different pattern when the scientists looked strictly at the 239 individuals diagnosed with dementia. Within this specific group, about 36 percent of the patients had depression.
In the dementia group, the newer Body Roundness Index showed a strong and consistent link to depressive symptoms. “What surprised us was that we did not find positive results for the measures most commonly recommended to screen for obesity, such as body mass index and waist circumference,” Sudo noted.
“In contrast, the Body Roundness Index, a newer measure, showed a meaningful association with depressive symptoms,” Sudo explained. “This suggests that body fat distribution may capture clinically relevant information that more traditional measures do not fully reflect in this population.”
The scientists divided the patients into four equal groups based on their Body Roundness Index scores. They found that those in the highest quarter of roundness scores had more than three times the odds of experiencing depression compared to those in the lowest quarter. This relationship held true even after the scientists adjusted their mathematical models to account for other factors like age, sex, education level, and existing health conditions.
“Our findings suggest that, in people with dementia, greater body fat accumulation may be linked to a higher risk of depressive symptoms,” Sudo said. “In other words, body composition may provide useful clues not only about physical health, but also about mental health in neurodegenerative conditions.”
“While this does not prove cause and effect, it highlights how closely emotional well-being and metabolic health may be connected in dementia,” Sudo continued. The researchers suggest that the Body Roundness Index provides a better reflection of central adiposity, which is the accumulation of fat around the belly and internal organs. This specific type of fat is highly active biologically and is known to release inflammatory chemicals into the bloodstream.
While this study provides new insights, there are a few limitations to consider. “This was a cross-sectional study, so it shows an association but does not allow us to determine cause and effect,” Sudo pointed out.
“In addition, the sample came from a memory clinic, which means the findings may not fully generalize to all older adults with dementia in the community or other clinical settings,” Sudo added. The researchers also relied on mathematical formulas rather than precise medical imaging. Future studies would benefit from using advanced body scans to confirm the exact amount and location of internal body fat.
“Our next step is to study these associations over time to see whether measures such as the Body Roundness Index can help predict depressive symptoms in dementia,” Sudo said. “More broadly, we are interested in understanding how nutritional factors relate to neuropsychiatric symptoms and other clinical features of dementia.”
“This includes examining associations between dietary patterns, body composition, and dementia symptoms, as well as the potential role of different food groups according to their degree of processing,” Sudo concluded. Integrating simple shape-based measurements into routine medical visits might eventually help doctors provide better care for vulnerable older adults.
The study, “Body roundness index as a predictor of depression in dementia: A cross-sectional study,” was authored by Clarissa Pacheco da Rocha Fernandes, Natalia Oliveira, Rejane Soares, Fernanda Rodrigues, Gabriel Bernardes, Raquel Quimas Molina da Costa, Naima Assuncao, Alina Teldeschi, Felippe Mendonca, Victor Calil, Andrea Silveira de Souza, Claudia Drummond, Fernanda Tovar-Moll, Paulo Mattos, and Felipe Kenji Sudo.
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