Obesity doesn’t just affect the body — it can also affect how your brain works. Many people may wonder if carrying extra weight, especially around the belly, is linked to dementia. If so, how does obesity increase the risk?

This article explains what dementia is, how it’s connected to obesity, and what steps you can take to support your brain health.

What Is Dementia?

Dementia isn’t a single disease — it’s a group of symptoms that affect memory, thinking, reasoning, and problem-solving abilities. Alzheimer’s disease is the No. 1 cause, but there are also other types, such as vascular dementia and Lewy body dementia. Each type affects the brain in a different way.

Symptoms of Dementia

Symptoms of dementia can be different for each person and type, but some common symptoms include:

• Memory loss that disrupts daily life
• Trouble solving problems or making decisions
• Confusion about time or place
• Difficulty speaking or writing clearly
• Changes in mood or personality

Although dementia typically affects older adults, it’s not a normal part of aging. Dementia is caused by damage to brain cells, which can happen for many reasons. For example, poor blood flow or a buildup of harmful proteins can interfere with how the brain works.

Does Obesity Contribute to Dementia?

Obesity is a medical condition in which a person’s body mass index (BMI), a measure of weight relative to height, is 30 or higher. BMI is just one tool that doctors use to understand a person’s health.

According to the Alzheimer’s Society, having obesity between the ages of 35 and 65 may raise the risk of dementia by roughly 30 percent. Researchers have identified several ways obesity can affect how the brain functions.

1. Inflammation

Obesity can lead to chronic (long-term) inflammation in the body, which means the immune system stays active even when there’s no infection or disease. Over time, this constant inflammation can damage blood vessels and brain cells, which may contribute to a higher risk of cognitive decline and dementia.

2. Insulin Resistance

Many people with obesity also have insulin resistance — their body’s cells don’t respond well to insulin, a hormone that helps turn sugar into energy. Visceral fat (fat around the belly and organs) plays a big role because it not only increases the risk of type 2 diabetes but also affects how the brain uses sugar. This can harm brain cells and lead to a buildup of proteins like amyloid plaques, which are linked to Alzheimer’s disease.

3. Vascular Damage

Obesity raises the risk of high blood pressure and atherosclerosis (a condition in which arteries become clogged with fatty deposits). Both conditions reduce blood flow to the brain, which means brain cells don’t get enough oxygen and nutrients. This can lead to vascular dementia, which is caused by poor circulation in the brain.

4. Brain Shrinkage

Studies have found that people with higher BMI may have smaller brains. This shrinkage could make the brain age faster, possibly by up to 10 years.

5. Other Health Problems

Obesity often comes with other health issues called comorbidities. The following comorbidities may also raise the risk of dementia:

• High blood pressure — May damage blood vessels in the brain
• Type 2 diabetes — Affects how the brain uses sugar and insulin
• High cholesterol — Can lead to plaque buildup in the arteries, reducing blood flow to the brain

Can Weight Loss Help Prevent Dementia?

While more research is needed, studies suggest that managing weight, especially during midlife, can improve attention and memory — two major parts of dementia.

The connection between dementia and weight is complex. Still, maintaining a healthy weight may lower your risk of developing dementia. Even small changes can make a difference — losing just 5 percent to 10 percent of extra body weight may help.

Some treatments for obesity, like weight loss surgery, may also lower dementia risk. A study from 2025 found that bariatric surgery may delay the start of Alzheimer’s disease and other types of dementia. A 2024 study showed that weight loss surgery might improve thinking skills and overall health.

Although these findings are encouraging, larger studies are needed to better understand how these treatments affect long-term brain health. It’s also important to remember that factors beyond weight can lead to an increased risk of dementia.

How Can You Lower Your Risk of Dementia?

If you’re living with obesity, you can take steps to protect your brain. There’s no guaranteed way to prevent dementia, but certain lifestyle changes may help lower your risk. Talk with your doctor to create a plan that fits your needs.

1. Stay Physically Active

Physical activity not only helps manage weight but also supports brain health by improving blood flow and reducing inflammation. Aim for about 150 minutes a week of moderate-intensity activities like walking, biking, and swimming. Your healthcare provider can help you choose the safest activities for you.

2. Eat a Balanced Diet

A healthy diet supports both your brain and body. Try to eat more fruits and vegetables, whole grains, lean proteins (like beans, fish, and poultry), and healthy fats (such as olive oil, avocados, and nuts). Limit sugar, salt, and processed foods, which may cause inflammation and harm brain function.

3. Manage Blood Sugar and Blood Pressure

Work with your doctor to keep your blood sugar and blood pressure in a healthy range. Higher blood sugar increases the risk of heart disease and type 2 diabetes, two conditions linked to dementia. High blood pressure can also damage blood vessels in the brain.

4. Get Enough Sleep

Good sleep helps your brain clear out waste and stay healthy. Aim for seven to eight hours of restful sleep each night. Poor sleep is tied to memory issues and faster brain aging. If you have sleep difficulties, such as insomnia or sleep apnea (a disorder that causes breathing to repeatedly stop and start during sleep), talk with your doctor.

5. Stay Mentally Sharp and Social

Keep your brain busy with activities like puzzles, reading, or learning new skills. Being mentally engaged can help the brain stay strong over time. Also, staying connected with friends and family may reduce feelings of loneliness, stress, or mental health concerns and reduce the risk of cognitive decline.

Obesity and dementia are both serious health conditions, but the good news is that you can take steps to reduce your risk. By staying active, managing your health, and making small daily changes, you can protect your brain and improve your overall well-being.

It’s never too late to start. Talk with your healthcare provider about a plan that works for you.

Talk With Others Who Understand

On MyObesityTeam, the social network for people with obesity and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with obesity.

What did you learn about the connection between obesity and dementia? What steps have you taken to reduce the risk of dementia? Share your experience in the comments below, or start a conversation by posting on your Activities page.