Obesity has long been linked to many health conditions, including cardiovascular disease, Type 2 diabetes, and some cancers. New research adds another concern: cognitive decline.
Researchers compared patterns of brain atrophy and amyloid-β/tau protein accumulation (hallmarks of Alzheimer’s) in patients with obesity and Alzheimer’s disease. They used a sample of over 1,300 individuals from four groups—Alzheimer’s disease patients, healthy people, obese but otherwise healthy people, and lean people.
The study was conducted using two large cohorts: the UK Biobank and the Alzheimer’s Disease Neuroimaging Initiative (ADNI).
Researchers used PET brain scans to investigate what mechanisms might be responsible for similarities between obesity-related brain atrophy and Alzheimer’s-related amyloid-beta accumulation. They also looked for overlapping areas among patients with these conditions.
The scans showed these groups experienced similar brain thinning in areas associated with learning, memory, and judgment.
Additional data were included from a previous study involving over 20,000 participants, which showed that increased body mass index (BMI), body fat percentage, and waist-to-hip ratio were associated with worse fluid intelligence (ability to solve problems) and working memory.
Earlier research also found that obesity can change the body in ways that are linked to increased Alzheimer’s risk, particularly damage to blood vessels in the brain and accumulation of abnormal proteins in the brain.
Obesity is related to many health problems, such as Type 2 diabetes, hypertension, and high cholesterol.
“All those affect the brain in a negative way,” study author Filip Morys, who holds a doctorate in cognitive neuroscience and who is a postdoctoral researcher at McGill University in Montreal, Canada, told The Epoch Times. “For example, through changes in the brain’s vascular system or the blood-brain barrier, this might in turn lead to neuronal loss.”
Obesity rates have increased alarmingly in the last decades, reaching global epidemic levels.
Obesity has tripled worldwide since 1975. World Health Organization (WHO) data from 2016 show that nearly 40 percent of adults 18 years and older were overweight, and 13 percent were obese.
From 1999 to 2000, through 2017 to March 2020, obesity prevalence in the United States rose from almost 31 percent to about 42 percent.
In the same period, the prevalence of severe obesity also nearly doubled.
Obesity is believed to increase neurodegenerative disease risk by two means—“promoting insulin resistance and the production of inflammatory molecules in the body called cytokines,” said Dr. Jonathan J. Rasouli, director of complex and adult spinal deformity surgery at Staten Island University Hospital, part of Northwell Health in New York.
The combination of these factors can mean an increased risk of cardiovascular, pulmonary, musculoskeletal, and neurologic diseases, he continued.
There’s evidence showing insulin plays a role in brain health, and insulin resistance, which is associated with overweight and obesity, is significantly associated with Alzheimer’s risk.
A study published in Frontiers in Neuroscience shows that in addition to metabolic functions, insulin also modifies neuronal activity that improves memory in mammals and promotes the health of synapses in the brain.
When the brain can’t use insulin properly, cognition can become impaired.
A recent study stated that insulin signaling is impaired in the brains of Alzheimer’s patients, and brain insulin resistance appears to be an early and common feature of Alzheimer’s disease.
Can weight loss reverse or prevent cognitive decline; is it ever too late? The impact of weight loss on cognitive function in older adults, specifically, is still not understood fully, and it’s likely that more research will be needed.
However, there is encouraging evidence that it may help.
A recent study finds that even modest weight loss can lead to improved cognitive function in older adults. Furthermore, lifestyle changes, like exercise and a healthy diet, will likely have a positive impact on cognitive function and overall health at any age.
When it comes to cognitive decline, “an ounce of prevention is worth a pound of cure,” said Rasouli.
Although the progression of cognitive decline—including memory loss—can be slowed or temporarily stopped, he warned that as soon as the process starts, it is very difficult to fully “return to normal” afterward.
Reducing sources of inflammation is one of the things Rasouli encourages patients to do.
Normal aging is associated with increased and prolonged inflammation throughout the body—and the brain.
There is evidence that persistent, increased levels of inflammation are strongly associated with neurodegeneration, impaired neuron growth (neurogenesis), and chronic diseases.
Metaflammation is a metabolic inflammatory state associated with obesity that directly contributes to insulin resistance, metabolic syndrome, and Type 2 diabetes. Evidence shows that losing weight can reverse this process.
Morys said the “key takeaway” is that obesity is a major risk factor for Alzheimer’s disease and other types of dementia.
“In line with this, we think that obesity prevention and weight loss might play a very important role in decreasing the risk for Alzheimer’s disease,” he concluded.