Good obesity? Healthy obesity reduces Alzheimer risk, study finds

A recent study published in the Alzheimer's-related journal Alzheimer's Research & Therapy found that relatively healthy obesity—defined as having no metabolic diseases or only one that meets the metabolic syndrome diagnostic criteria—may lower the risk of developing Alzheimer's disease. Professor Kang Seong-hoon of the Neurology Department at Korea University Guro Hospital and his research team conducted the study to analyze whether the degree of cognitive decline differs among obese patients based on the presence of metabolic syndrome.

The study was conducted on 1,736 South Koreans aged 45 and older without dementia. The research team classified participants into groups based on body mass index (BMI): underweight (BMI less than 18.5), normal weight (BMI 18.5 to 24.9), and obese (BMI 25 or higher). Each group was further divided based on metabolic syndrome criteria into a metabolically healthy group and a metabolic syndrome group. The metabolically healthy group was defined as having one or fewer metabolic syndrome diagnostic criteria—hypertension, high fasting blood sugar, high triglycerides, low HDL cholesterol—excluding waist circumference.

The researchers analyzed amyloid PET scans, brain MRI results, and cognitive function test results of the participants. The positive rate of amyloid beta protein, indicating the risk of Alzheimer's disease-causing substance accumulation, was higher in the underweight group (73.9%) than in the obesity group (37.0%), suggesting that obesity may reduce amyloid accumulation. In contrast, the metabolic syndrome obesity group had a higher accumulation rate of 42.5%. The effect of obesity in preventing amyloid accumulation was only significant in the metabolically healthy group.

In the absence of metabolic syndrome, the accumulation of amyloid beta protein is lower, with a positive rate of 29.6% in the metabolically healthy obesity group. Long-term follow-up showed that the rate of cognitive decline was slowest in the metabolically healthy obesity group. Furthermore, the metabolically healthy obesity group had thicker hippocampal volumes and higher cognitive function scores.

"The study confirmed that the presence or absence of metabolic syndrome affects the relationship between weight and Alzheimer's markers," Professor Kang Seong-hoon stated, according to the Digital Chosun. "Considering that weight and metabolic syndrome can be corrected through diet, exercise, and medication, maintaining metabolic health and appropriate weight can contribute to preventing Alzheimer's-related dementia," he said, according to Asia Economy. 

Professor Kang is the director of the Alzheimer's Prevention Center recently opened at Korea University Guro Hospital. "Based on this research result, by accompanying appropriate lifestyle corrections, we expect to maximize the therapeutic effect of the Alzheimer's disease prevention new drug being introduced in the country at the end of this year," he added, according to Sports Chosun.

The findings reveal that healthy obesity, defined as having a BMI of 25 kg/m² or higher without metabolic diseases or with only one metabolic disease, is associated with a lower risk of developing Alzheimer's disease. Preventing dementia is possible through lifestyle corrections. 

While the correlation between weight and Alzheimer's disease markers was previously known, no research had comprehensively considered the impact of obesity and metabolic syndrome on these markers. The research team revealed the effects of weight and metabolic syndrome on the accumulation and progression of Alzheimer's disease-causing substances. The correlation between BMI and Alzheimer's disease markers has been confirmed through various studies. It is determined that the higher the accumulation of amyloid beta protein confirmed by amyloid PET, the higher the risk of developing Alzheimer's disease.

In South Korea, a BMI of 25 or higher is considered obesity. Obesity, known as the root of many diseases, is said to increase the risk of developing dementia. However, this study suggests that the relationship between obesity and Alzheimer's disease is more nuanced. The analysis showed that the obese group had lower amyloid accumulation compared to other groups. The effect of obesity in preventing amyloid accumulation was only significant in the metabolically healthy group.

Sources: Sports Chosun, Segye, Asia Economy, Digital Chosun

This article was written in collaboration with generative AI company Alchemiq