Overweight people who lose weight without dieting after age 65 are at high risk for dementia (Age and Ageing, May 2019;48(3):367–373). For 15 years, the authors followed 257,523 overweight but otherwise healthy people and compared them to 161,927 people who had cancer, heart failure or multiple diseases. People in the healthy group who lost weight for no apparent reason were at significantly higher risk for dementia than people in the group with major health problems. When people start to develop dementia, they often lose their appetites and eat far less.

Excess weight is a major risk factor for dementia (Neurology, 2011;76:1568–1574). In a review of 16 studies on the subject, 13 of them showed that excess weight is associated with increased risk for dementia. The three studies that showed no association between obesity and dementia did not measure weight loss in later life (J Alzheimer’s Dis, 2019;70(Suppl 1):S87–S99).

Dementia is associated with decreased brain volume, and obese middle-aged people have the greatest loss of parts of the brain that control memory. Doctors took MRIs of the brains of 9,652 men and women, average age 55, and found that those who were overweight had the smallest amount of brain grey matter which is characteristic of dementia. Brain grey matter controls muscles, sensory perception such as seeing and hearing, memory, emotions, speech, decision making, and self-control. The authors used waist-to-height ratios to show that people who stored most of the fat in their bellies had the smallest amount of grey matter (Neurology, February 05, 2019;92(6)).

Inflammation from Obesity Damages the Brain
Obesity turns on your immune system and keeps it active all the time, which is called inflammation (Arch Med Sci, Jun 2017;13(4):851–863). Many studies show that excess weight is associated with inflammation that can damage your brain (Alzheimer’s Disease, August 4, 2020; 1-7).

Inflammation damages arteries throughout your body by increasing clotting, forming plaques in arteries, and causing insulin resistance, leading to diabetes. Anything that damages your arteries can also damage your brain. For example:
• People who have had heart attacks are at 35 percent increased risk for suffering vascular dementia, and the risk remains elevated for up to 35 years after the heart attack (Circulation, 2018;137(6):567–577).
• The largest brain imaging study ever of more than 17,000 subjects showed that the fatter the middle-aged person, the greater the reduction in blood flow, particularly to the parts of the brain damaged most by Alzheimer’s disease: the temporal lobe, parietal lobe, hippocampus, posterior cingulate, and precuneus (J Alzheimer’s Disease, Aug 4, 2020;1-17).

My Recommendations
Obese people over age 65 who lose weight without trying are at significant risk for dementia. The weight loss is often caused by loss of appetite, which is an early sign of the onset of dementia. However, people who purposely lose weight with a healthful diet and exercise program are at reduced risk for dementia (Neurosci Biobehav Rev, 2017;72:87–94).

Obesity is primarily a faulty lifestyle disease caused by eating too much and exercising too little, although some people are far more susceptible genetically than others. You can lose excess weight by following an anti-inflammatory lifestyle that includes:
• eating lots of fruits, vegetables, whole grains, beans, seeds and nuts
• severely restricting red meat, processed meats, sugar-added foods and sugared drinks, and limiting foods made with refined grains and other refined carbohydrates
• trying to exercise every day

Note: I did a radio show this week on WRTA in Altoona PA, discussing this study, COVID-19, and many other topics. You can listen here: https://soundcloud.com/talkradio985/dr-gabe-mirkin-august-2020-wrtas-the-11th-hour-with-doug-herendeen