World first study links obesity with reduced brain plasticity

September 24, 2020

Science Daily/University of South Australia

A world-first study has found that severely overweight people are less likely to be able to re-wire their brains and find new neural pathways, a discovery that has significant implications for people recovering from a stroke or brain injury.

In a new paper published in Brain Sciences, researchers from UniSA and Deakin University show that brain plasticity is impaired in obese people, making it less likely that they can learn new tasks or remember things.

Using a series of experiments involving transcranial magnetic stimulation, the researchers tested 15 obese people aged between 18 and 60, comparing them with 15 people in a healthy-weight control group.

Repeated pulses of electrical stimulation were applied to the brain to see how strongly it responded. The healthy-weight control group recorded significant neural activity in response to the stimulation, suggesting a normal brain plasticity response. In contrast, the response in the obese group was minimal, suggesting its capacity to change was impaired.

UniSA researcher Dr Brenton Hordacre says the findings provide the first physiological evidence of a link between obesity and reduced brain plasticity.

Obesity is based on body mass index (BMI) which calculates the ratio between height and weight to determine body fat. An adult who has a BMI between 25 and 29.9 is considered overweight. Anything above that is obese.

"Obesity is already associated with a raft of adverse health effects, including a higher risk of cardiovascular disease, metabolic disorders and dementia," Dr Hordacre says.

"For the first time, we found that obesity was associated with impaired brain function, adding further support for the need to address the obesity epidemic.

"A growing number of people are obese -- 650 million according to the World Health Organization -- which not only has health consequences but is a serious financial burden for global health systems," he says.

"These new findings suggest that losing weight is particularly important for healthy brain ageing or for recovery in people who suffer strokes or brain injuries, where learning is fundamental for recovery."

Stroke is the third most common cause of death in Australia and the leading cause of disability, affecting speech, cognition and memory.

The ability of the brain to find new pathways is crucial to recovery, Dr Hordacre says. Worldwide, 15 million people suffer strokes each year, a third of whom die.

https://www.sciencedaily.com/releases/2020/09/200924101936.htm

The effects of obesity mirror those of aging

Researchers identify a shared list of health issues, from DNA damage to cognitive decline

February 25, 2020

Science Daily/Concordia University

Researchers argue that obesity should be considered premature aging. They look at how obesity predisposes people to acquiring the kinds of potentially life-altering or life-threatening diseases normally seen in older individuals: compromised genomes, weakened immune systems, decreased cognition, increased chances of developing type 2 diabetes, Alzheimer's disease, cardiovascular disease, cancer and other illnesses.

Globally, an estimated 1.9 billion adults and 380 million children are overweight or obese. According to the World Health Organization, more people are dying from being overweight than underweight. Researchers at Concordia are urging health authorities to rethink their approach to obesity.

In their paper published in the journal Obesity Reviews, the researchers argue that obesity should be considered premature aging. They look at how obesity predisposes people to acquiring the kinds of potentially life-altering or life-threatening diseases normally seen in older individuals: compromised genomes, weakened immune systems, decreased cognition, increased chances of developing type 2 diabetes, Alzheimer's disease, cardiovascular disease, cancer and other illnesses.

The study was led by Sylvia Santosa, associate professor of health, kinesiology and applied physiology in the Faculty of Arts and Science. She and her colleagues reviewed more than 200 papers that looked at obesity's effects, from the level of the cell to tissue to the entire body. The study was co-authored by Bjorn Tam, Horizon postdoctoral fellow, and José Morais, an associate professor in the Department of Medicine at McGill University.

"We are trying to comprehensively make the argument that obesity parallels aging," explains Santosa, a Tier II Canada Research Chair in Clinical Nutrition. "Indeed, the mechanisms by which the comorbidities of obesity and aging develop are very similar."

From cells to systems

The paper looks at ways obesity ages the body from several different perspectives. Many previous studies have already linked obesity to premature death. But the researchers note that at the lowest levels inside the human body, obesity is a factor that directly accelerates the mechanisms of aging.

For instance, Santosa and her colleagues look at the processes of cell death and the maintenance of healthy cells -- apoptosis and autophagy, respectively -- that are usually associated with aging.

Studies have shown that obesity-induced apoptosis has been seen in mice hearts, livers, kidneys, neurons, inner ears and retinas. Obesity also inhibits autophagy, which can lead to cancer, cardiovascular disease, type 2 diabetes and Alzheimer's.

At the genetic level, the researchers write that obesity influences a number of alterations associated with aging. These include the shortening of protective caps found on the ends of chromosomes, called telomeres. Telomeres in patients with obesity can be more than 25 per cent shorter than those seen in control patients, for instance.

Santosa and her colleagues further point out that obesity's effects on cognitive decline, mobility, hypertension and stress are all similar to those of aging.

Pulling out from the cellular level, the researchers say obesity plays a significant role in the body's fight against age-related diseases. Obesity, they write, speeds up the aging of the immune system by targeting different immune cells, and that later weight reduction will not always reverse the process.

The effects of obesity on the immune system, in turn, affect susceptibility to diseases like influenza, which often affects patients with obesity at a higher rate than normal-weight individuals. They are also at higher risk of sarcopenia, a disease usually associated with aging that features a progressive decline in muscle mass and strength.

Finally, the paper spells out how individuals with obesity are more susceptible to diseases closely associated with later-life onset, such as type 2 diabetes, Alzheimer's and various forms of cancer.

Similarities too big to ignore

Santosa says the inspiration for this study came to her when she realized how many children with obesity were developing adult-onset conditions of diseases, such as hypertension, high cholesterol and type 2 diabetes. She also realized that the comorbidities of obesity were similar to that of aging.

"I ask people to list as many comorbidities of obesity as they can," Santosa says. "Then I ask how many of those comorbidities are associated with aging. Most people will say, all of them. There is certainly something that is happening in obesity that is accelerating our aging process.'"

She thinks this research will help people better understand how obesity works and stimulate ideas on how to treat it.

"I'm hoping that these observations will focus our approach to understanding obesity a little more, and at the same time allow us to think of obesity in different ways. We're asking different types of questions than that which have traditionally been asked."

https://www.sciencedaily.com/releases/2020/02/200225122954.htm

Being a car commuter with obesity linked to a 32% increased early death risk

April 27, 2019

Science Daily/European Association for the Study of Obesity

New research presented at this year's European Congress on Obesity in Glasgow, Scotland (28 April -- 1 May) shows that individuals with obesity who commute by car have a 32% higher risk of death, from any cause, compared with those individuals with a normal weight and commute via cycling and walking. The study is by Edward Toke-Bjolgerud, University of Glasgow, UK, and colleagues.

Previous work, using UK Biobank data, has shown that active commuting, mainly cycling, was associated with a 50% lower risk of death, from any cause, and heart disease compared to car commuting. Since 57% of men and 66% of women in the UK are overweight or obese -- a condition linked with a range of poor health outcomes -- the authors of this new research aimed to investigate how different modes of active commuting (car, cycling, walking, mixed-mode) might alter the association between obesity and adverse health outcomes.

Their analysis includes 163,149 UK Biobank participants who have been followed up for a mean of 5 years. The age range was 37 to 73 years and 50.8% were women. Obesity was defined as a body mass index (BMI) (kg/m2) of greater than 30. Active commuting to and from work was self-reported and people classified in one of the following groups: car commuters, walking and cycling (active-mixed), cycling-only and walking-only. The health outcomes of interest were death from any cause, death due to heart disease and hospital admission due to non-fatal heart disease.

Dr Carlos Celis, from the British Heart Foundation Glasgow Cardiovascular Research Centre at the University of Glasgow and lead investigator of this work, reported that during the follow-up a total of 2,425 participants died and 7,973 developed heart disease. Compared with having a healthy body weight and reported mixed active commuting (walking and cycling to and from work; reference group), being obese combined with car commuting was associated with a 32% higher risk for premature death, a doubling of risk of heart disease mortality and a 59% increase in risk non-fatal heart diseases.

In contrast, those people with obesity who reported being active commuters had a risk of death from any cause that was similar to normal weight active commuters, suggesting that cycling or walking to and from work could reduce the detrimental effect of obesity. However, the risk of heart disease was still increased by 82% in active commuters with obesity compared with normal weight active commuters.

The authors conclude: "Our findings, if causal, suggest that people with overweight or obesity could potentially decrease the risk of premature mortality if they engage in active commuting."

They add: "Regardless of your body weight, being physically active could partly reduce the excess risk associated with obesity. However, compared to other forms of physical activity -- such as gyms and exercises classes -- active commuting can be implemented and fitted within our daily routines, often with no additional cost, but at the same time could increase our overall physical activity levels and therefore help to meet the current physical activity recommendations for health."

https://www.sciencedaily.com/releases/2019/04/190427201946.htm