Study links weight and Alzheimer’s

The link between obesity and Alzheimer’s disease has been confirmed by a new study that concludes “weight hurts the brain”.

In May, YourLifeChoices reported on an Australian study that found a link between obesity and shrinkage in an area of the brain responsible for memory and learning – the hippocampus.

The new study, published in the Journal of Alzheimer’s Disease, analysed blood flow in the brain. It categorised participants on the basis of their body mass index (BMI), which divides height by weight.

As Science Daily put it: “Low cerebral blood flow is the number one brain imaging predictor that a person will develop Alzheimer’s disease. It is also associated with depression, ADHD, bipolar disorder, schizophrenia, traumatic brain injury, addiction, suicide, and other conditions.”

Participants classified as overweight, obese and morbidly obese had lower blood flow to virtually all brain regions, including the temporal lobes and the hippocampus. The researchers found that blood flow to the brain worsened as BMI increased.

Low brain blood flow was noted in participants in a resting state and while undertaking concentration tasks.

“This study shows that being overweight or obese seriously impacts brain activity and increases the risk for Alzheimer’s disease as well as many other psychiatric and cognitive conditions,” explained Daniel G. Amen, MD, the study’s lead.

One in three Australians were obese in 2017–2018, says the Australian Institute of Health and Welfare (AIHW), up from 19 per cent in 1995.

The AIHW says excess weight, especially obesity, is a major risk factor for cardiovascular disease, type 2 diabetes, high blood pressure, sleep apnoea, psychological issues, some musculoskeletal conditions and some cancers.

“As the level of excess weight increases, so does the risk of developing these conditions.” 

Obesity is defined as “a treatable disease that is a worldwide health concern associated with having an excess amount of body fat”.

Advocacy site obesityaction.org says obesity is “caused by genetic and environmental factors and can be difficult to control through dieting alone”.

George Perry, PhD, editor-in-chief of the Journal of Alzheimer’s Disease, said: “Acceptance that Alzheimer’s disease is a lifestyle disease, little different from other age-related diseases, that is the sum of a lifetime is the most important breakthrough of the decade. Dr Amen and collaborators provide compelling evidence that obesity alters blood supply to the brain to shrink the brain and promote Alzheimer’s disease. This is a major advance because it directly demonstrates how the brain responds to our body.”

The study underlines excess weight as one of the major issues facing the health of the Western world. However, Dr Amen sees hope.

“One of the most important lessons we have learnt through 30 years of performing functional brain imaging studies is that brains can be improved when you put them in a healing environment by adopting brain-healthy habits, such as a healthy calorie-smart diet and regular exercise.”

He believes the findings prove people have way more control than they think over developing Alzheimer’s disease.

“Weight hurts the brain. I want people to care enough about their brains that they will work to get their bodies healthy,” says Dr Amen.

Another study, published in February, argued that “obesity should be considered premature ageing because of its strong association to chronic health issues that typically appear in old age, like weaker immune systems, cognitive decline, Alzheimer’s and cardiovascular disease”.

In the study, the researchers examined over 200 papers reporting the effects of obesity on every part of the body. They concluded that the health impact of obesity mirrors ageing: impaired genomes and mitochondrial function, a weaker immune system and chronic inflammation.

Obesity even affected the cellular level, harming mitochondrial DNA integrity and telomeres, which are associated with life expectancy and ageing.

“I ask people to list as many co-morbidities of obesity as they can,” said Sylvia Santosa, an associate professor of health, kinesiology, and applied physiology at Concordia University.

“Then I ask how many of those co-morbidities are associated with ageing. Most people will say, all of them. There is certainly something that is happening in obesity that is accelerating our ageing process.”

Health website beingpatient.com says recent studies linked obesity with the risk of developing dementia and larger waist size and higher blood pressure can contribute to cognitive decline and dementia.

“The ways in which obesity is linked to Alzheimer’s are many and varied — and researchers are still exploring all the complex ways weight, heart health and physical inactivity impact the brain. One thing many experts do agree on, however, is that exercise and diet can have a significant effect on brain health — and these lifestyle changes may prevent dementia, or at least slow its progression.”

Are you worried about your weight? Do you know your BMI? Have you noted any correlation between weight and memory issues in older friends or family?

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Written by Will Brodie

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