Changes to our bodies and brains are totally normal as we age. And, we know the brain is arguably the most important organ—it controls and coordinates actions and reactions, allows us to think and feel, and enables us to have memories and feelings—all the things that make us human.

The health of our brains affects our overall health, and interestingly enough, a 2020 study found that our weight is associated with how our brain functions. More experts are beginning to understand the relationship between obesity and the brain. The striking new evidence has shed light on how obesity impacts the brain, but it also shows ways to reverse the effects. Here’s how.

Excess weight has been associated with impaired memory, the ability to pay attention, and the decision-making process, according to a 2015 literature review written by Australian researchers. Small tasks that take a certain attention span may take more effort, and problem-solving, intuition, or creativity can be stunted. Skills we need to process daily events may be disrupted or fractured when we have higher body fat. Simple things like making the healthiest food choices or trying to figure out that important question at work can become more difficult when we have extra body fat.

Functions like cognition, motor performance, and brain plasticity are crucial in keeping us performing at optimal levels of “human-ness.” The brain's plasticity is the ability to change at any age—think of it as improved skills like learning that new move in yoga, or conversely, weakened skills like forgetting the name of the person you just met.

Synaptic plasticity (brain plasticity) controls how effectively two neurons communicate with each other according to the Queensland Brain Institute at The University of Queensland, and neurons control literally everything we do. Healthy neurons relay information faster and more efficiently—improving and understanding a physical skill or helping with memory loss. And interestingly, synaptic plasticity was reduced in obese adults compared to healthy weight adults explained in a 2020 study in the Brain Science Journal.

Alzheimer’s disease (AD) is a brain disorder that slowly destroys memory and thinking skills and, eventually, the ability to do the simplest tasks. It’s devastating to the people who’ve been diagnosed, as well as their families and friends, and it’s scary to think of one day either having it or caring for a loved one that does.

The link between obesity became clear when in 2011, evidence-supported risk factors for AD included low education, smoking, physical inactivity, depression, mid-life hypertension, diabetes, and mid-life obesity reported by the National Institutes of Health (NIH). Another large study found that these risk factors contribute to up to half of the AD cases globally (17.2 million) and in the US (2.9 million).

Even more recently, research emerged in 2020 explaining that obesity is associated with reduced blood flow to the brain, and this may help explain why obesity is associated with an increased risk for Alzheimer’s disease.

Researchers did brain scans on 17,721 men and women with an average age of 41, tracking blood flow in 128 regions of the brain. They found that the higher the Body Mass Index (BMI), the lower the blood flow to five regions of the brain that are especially vulnerable in Alzheimer’s disease: the temporal lobes, the parietal lobes, the hippocampus, the posterior cingulate, and the precuneus. Their work cemented the link between excess weight and Alzheimer’s.

Having too much body fat can threaten the brain and lead to a stroke, also known as a brain attack, which happens when something blocks a blood vessel to the brain. The blood vessel needs to be able to carry oxygen and nutrients to the brain, and when that doesn’t happen, extensive damage to our brains and body occurs. Even more frightening, many people die from having a stroke if medical attention isn’t received within a few hours. A body mass index (BMI) of 30 or higher—which is an indicator of obesity—increases the risk for ischemic strokes by 50 to 100 percent, according to a 2021 guideline from the American Stroke Association. 

In addition, in 2017, a study of 813 people across the United States and Europe found that those with obesity were twice as likely to have a stroke compared with those with a healthy BMI. This increased risk of stroke is linked to other complications often associated with obesity, including diabetes and hypertension/high blood pressure (Horn et al. 2021).

Of course, more research needs to be done on the brain and the impact of excess weight, but researchers have found a proverbial “light at the end of the tunnel,” and ways to improve health and reverse the effects.

Movement is important for our hearts, muscles, and improving oxygen and blood flow. Physical activity is essential, even for those with limited mobility, according to Aliza Ben-Zacharia, Ph.D., DNP, assistant professor at the Hunter College School of Nursing in New York City. She recommends chair pedal exercisers, hand weights, swimming, or water workouts for her patients in wheelchairs or with leg weakness.

“Patients who experience pain and fatigue can ask their doctors for a physical assessment and assistance in tailoring an appropriate plan,” Dr. Ben-Zacharia said in an article for the American Academy of Neurology. Additionally, “substantial evidence has suggested exercise to be an effective way to improve obesity and related cognitive and motor dysfunctions,” suggested a 2016 study published in the Journal Neural Plasticity. There’s a direct link between the amount we move and a decreased risk for Alzheimer’s or even building better brain plasticity.

Cutting back on saturated fat—the kind found in red meat, whole milk, and butter—is good for brain cells, asserts Eva Feldman, MD, Ph.D., FAAN, endowed professor of neurology at the University of Michigan Medical School in Ann Arbor and her team. In a 2016 study published in PLoS One, she and her colleagues found that when mice were fed diets high in saturated fat, they quickly became obese and their memory worsened. When returned to a normal diet, the mice lost girth and regained their memory.

Even more, a study by Dr. Feldman's team published in the Journal of Neuroscience in May 2021 linked saturated fat and obesity to peripheral neuropathy—damage to nerves around the brain and spinal cord that can cause numbness and tingling.

In an American Academy of Neurology article, she encourages patients to eat more produce, nuts, whole grains, fish, poultry, and healthy fats such as olive oil. Eating a diet with more whole foods and less processed sugar or fat is an option for treating the effects of obesity, another study in 2018 by the National Institutes of Health notes.