ALZHEIMER’S AND OBESITY: IS THERE A LINK?
Obesity can cause several chronic diseases, such as heart disease, diabetes, high blood pressure, and cancer. It can also affect the brain’s structure and functions and cause neurological disorders.
Researchers even found a strong association between obesity and Alzheimer’s disease and dementia.
Upon further investigation, they found that obesity can cause neurodegeneration through several mechanisms involving increased inflammation, hormonal changes, and restricted blood flow to the brain.
Therefore, scientists concluded that reducing the body’s BMI and managing obesity can slow cognitive decline and lower the risk of Alzheimer’s and dementia when a person ages.
Continue reading to learn more about the effects of obesity on the brain and how it can increase the risk of Alzheimer’s disease.
How Does Alzheimer’s Disease Affect The Brain?
Alzheimer’s is a neurodegenerative disorder that affects the brain areas responsible for memory, thinking, language, and behavior. It is a progressive disease (it gets worse over time) and is the most common cause of dementia among older adults.
Alzheimer’s can cause memory loss, impaired thinking, and eventually losing the ability to carry out day-to-day tasks. This disease occurs when nerve cells (neurons) in the brain die.
A healthy human brain is made up of billions of neurons that use electrical and chemical signals to transmit information across different brain parts and between the brain and other body parts.
In Alzheimer’s disease, the brain proteins do not function as they usually do, which disrupts the connection between the nerve cells and causes the brain to shrink (brain atrophy). The neurons become damaged and eventually die.
How Does Obesity Affect The Brain?
Obesity is when the body accumulates excessive fatty (adipose) tissue. It is a prominent global health problem that can raise your chance of developing a number of chronic illnesses, including type 2 diabetes, heart disease, and cancer.
Substantial research suggests that obesity can negatively affect brain functions, including language, memory, learning, information processing, and psychomotor function.
Scientists found that obesity directly affects the brain’s central nervous system (CNS). They call it “the cross-talk between adipose tissue and the central nervous system” and believe this is why obese people have a higher risk of developing cognitive disorders.
Additionally, studies show that people who were obese had significantly smaller total brain volumes and reduced gray matter (GM).
When researchers investigated the association between obesity and brain structure abnormalities, they discovered abnormal cortical and subcortical thickness in the brains of people who are obese.
Scientists showed that obesity causes abnormal metabolism, increases inflammation, and alters hormonal signaling, all of which can damage the functioning of the brain’s neurons.
What Is The Link Between Obesity And Alzheimer’s?
Scientists have established a connection between obesity and dementia caused by Alzheimer’s disease. Several studies have shown that being obese or overweight increases the risk of Alzheimer’s and subsequent dementia, especially in women.
A study in Germany found that women with dementia between the ages of 79 and 88 years were overweight and had a higher average BMI at ages 70, 75, and 79 years than women without dementia.
Another study showed that obesity in mid-life is positively associated with later dementia. In the study, obese people aged <65 years were 1.4 times more likely to develop dementia later in life.
Research also revealed that people with a very high BMI in midlife had a 1.35 higher risk of developing Alzheimer’s disease and a 1.26 higher risk of developing dementia.
Additionally, population-based studies identified that an increased BMI significantly increases the risk of dementia, commonly caused by Alzheimer’s.
How Can Obesity Cause Alzheimer’s?
Recently, scientists are beginning to understand the direct effects of obesity on the brain’s central nervous system and how it can lead to Alzheimer’s.
They discovered that the buildup of fatty tissue and the metabolic diseases associated with obesity could damage cognition and increase the risk of developing Alzheimer’s.
For example, research showed that obesity-associated hypertension and diabetes could cause cerebrovascular (brain) disease. In turn, cerebrovascular disease causes cortical thinning, similar to Alzheimer’s disease, and loss of cognitive functions. The authors concluded that obesity management or losing weight could help prevent Alzheimer’s and late-life dementia.
Additionally, adipokines or adipocytokines are cell-signaling molecules produced by fatty tissue. Leptin, adiponectin, and interleukin-6 are the molecules that are essential for regulating metabolism, fat distribution, blood pressure, and inflammation.
Obesity causes the body to increase its production of adipokines. Research shows that adipokines can cross the blood-brain barrier and affect the brain’s central nervous system.
One of these adipokines, leptin, is involved in several brain functions, including the following:
- Brain development
- Neurogenesis (new neuron formation)
- Neuronal protection (preventing the brain’s neurons from dying)
- Synaptic functions (communication between two neurons or a neuron and a muscle cell)
Triglyceride levels are higher in fat or overweight people. Studies suggest that triglycerides can block leptin signaling in the brain and disrupt its neurophysiological functions, eventually leading to Alzheimer’s.
Increased body fat can also decrease blood supply to the brain, causing the death of brain cells. This is another way obesity can increase the risk of Alzheimer’s and dementia later in life.
Moreover, excess fatty tissues increase the production of proinflammatory cytokines, such as interleukin 1. That can lead to systemic and central inflammation, which could result in neuroinflammation in the brain. Inflammation suppresses the function of neurons in the brain and consequently causes cognitive impairment.
Furthermore, obesity is associated with reduced levels of brain-derived neurotrophic factor (BDNF), which supports the survival of neurons in the brain. Reduced BDNF signaling can damage cognitive functions, including memory and learning abilities.
Scientific evidence suggests that obesity can reduce cognitive functions, shrink the brain, change brain structures, and eventually cause Alzheimer’s and dementia. This happens primarily because of excessive fat tissue buildup, which causes changes in the body’s composition and the brain.
Therefore, interventions that reduce weight and improve physical health may help improve cognitive health and delay or prevent the onset of Alzheimer’s and dementia.
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- Alzheimer’s Disease: Etiology, Neuropathology, and Pathogenesis
- Obesity and Brain Function: The Brain–Body Crosstalk - PMC
- Brain-derived neurotrophic factor and its clinical implications - PMC
- The Role of Leptin and Adiponectin in Obesity-Associated Cognitive Decline and Alzheimer’s Disease
- Does Obesity Increase the Risk of Dementia: A Literature Review - PMC
- Obesity-Associated Neurodegeneration Pattern Mimics Alzheimer’s Disease in an Observational Cohort Study - IOS Press
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