By Richard Restak, M.D., George Washington University School of Medicine and Health Sciences

Edited by Kate Findley, The Great Courses Daily

When you gain too much weight, not only does your body slow down, but your brain also declines. Dr. Richard Restak explains the connection between obesity and Alzheimer’s and provides simple actions you can take to preserve your brain.

Poor Diet Impacts Brain Health

Your diet is critically important to your brain health. Eating the right foods and maintaining a proper weight will help you to avoid the harmful cognitive effects associated with obesity.  

Animal research shows that diets high in saturated fats lead to underperformance on memory tests. In tests involving reinforcing rewards such as pressing a button to get food, animals exhibit delayed reactions. 

Research with humans suggests that high cholesterol and obesity are risk factors for Alzheimer’s. This has huge implications for a nation with a penchant for fast food; two-thirds of us are overweight and 30 percent of us are obese. 

The latest research links addiction to obesity. High-fat, high-calorie diets decrease the responsiveness of the brain’s pleasure centers. 

Eating is associated with the release of dopamine, and the more dopamine released, the greater the degree of pleasure. People with fewer dopamine receptors tend to take in more food to experience pleasure. Unwittingly, their brains act the same way that an addict’s brain does, requiring more and more stimulus to achieve a similar pleasurable effect.

Benefits of Calorie Restriction

Therefore, eliminating obesity isn’t always easy, but it’s worth the effort because of obesity’s effects on the brain. Sixty-five years of animal research show that the rate of degenerative disease is slowed by caloric restriction—a balanced reduction of protein, fat, and carbs without reduction of nutrient content. 

Animals that eat 35 percent fewer calories not only live 35 percent longer, they live healthier lives, with lower rates of Alzheimer’s. They also cognitively outperform animals on unrestricted diets. For example, an Oregon Health and Science research study showed that caloric restriction combined with periodic fasting led to better learning and memory performance and exploration of surroundings.

Would a severely decreased caloric diet work for humans? A National Institute of Aging study showed that a 25-percent caloric restriction resulted in a lowering of body temperature and insulin levels. However, few people would be willing to conform to such a diet. 

Despite the evidence to suggest that caloric restriction of 800­ to 900 calories per day might have a similar effect in humans, it’s not feasible or easy to do. Fortunately, such severe restriction may not be necessary. 

Eliminating Harmful Foods

Keeping calories low enough to prevent obesity may be sufficient. Abide by “Primum non nocere,” which is Latin for “first do no harm.” 

Start by eliminating foods proven to cause harm. These include trans fats, which are formed when liquid oils are transformed into solid fats by adding hydrogen to vegetable oil. They were introduced to prolong the shelf life in crackers, cookies, and snack foods. 

Hydrogenated fats clog arteries in the brain and heart, leading to cognitive decline and memory loss. The stiffer and harder the fat—varying with degree of hydrogenation—the more clogging of blood vessels, like grease on the kitchen sink drain. Avoid food with “hydrogenated” or “partially hydrogenated” on the label.

You should also steer clear of fast foods such as fried chicken, fried fish, biscuits, French fries, potato chips, doughnuts, and muffins. Substitute with foods such as fruits, vegetables, chicken, whole-grain breads, and green leafy vegetables.

Brain-Friendly Foods 

Next, you should start eating foods with antioxidants, which are chemicals that interrupt oxidation. Think of the rusting of steel beams in a building.

A similar breakdown process occurs in the body. This is caused by free radicals, which are molecular fragments with one unpaired electron. These unstable fragments attract electrons from body tissues such as cell membranes and the structural components of the cell’s interior. 

The membranes or structural components are destroyed by the electron loss, and DNA is eventually attacked. This free radical damage to DNA is partly responsible for aging. 

Luckily, antioxidants in vegetables can dramatically protect against free radical damage. One study showed that older people eating more than two vegetable servings a day performed as well on cognitive tests as people five years younger—this held up over a six-year follow up. 

Finally, you can eat Omega-3 unsaturated fatty acids, found in oily fish like mackerel, salmon, trout, herring, and sardines. Psychiatrists noted that people living in Japan and Taiwan were 60 percent less likely to be depressed as compared to people in the United States, where at that time fish was not a staple food. 

Today psychiatrists prescribe Omega-3 as an antidepressant. It’s better that you get Omega-3 from fish than from supplements—eating fish provides lean, high-quality protein; vitamins; and minerals like selenium, off of which are not usually found in supplements. Two servings a week of fish is sufficient. 

Omega-3s also improve mental clarity. Clinical trial data showed that early-stage Alzheimer’s improved in patients who switched to a fish diet. 

All of this advice for better brain health is found in one diet, called the Mediterranean Diet, which consists of vegetables, fruits, legumes, cereals, olive oil, and fish. While it is low on meat and dairy products, it does allow for moderate amounts of red wine—in fact, it’s encouraged.

This article was edited by Kate Findley, Writer for The Great Courses Daily.

Dr. Richard Restak is Clinical Professor of Neurology at The George Washington University School of Medicine and Health Sciences. He earned his M.D. from Georgetown University School of Medicine. Professor Restak also maintains an active private practice in neurology and neuropsychiatry in Washington, D.C.