MRI reveals brain damage in obese teens
November 25, 2019
Science Daily/Radiological Society of North America
Researchers using MRI have found signs of damage that may be related to inflammation in the brains of obese adolescents, according to a study being presented next week at the annual meeting of the Radiological Society of North America (RSNA).
Obesity in young people has become a significant public health problem. In the U.S., the percentage of children and adolescents affected by obesity has more than tripled since the 1970s, according to the Centers for Disease Control and Prevention. Data from the World Health Organization indicates that the number of overweight or obese infants and young children ages five years or younger increased from 32 million globally in 1990 to 41 million in 2016.
While obesity is primarily associated with weight gain, recent evidence suggests that the disease triggers inflammation in the nervous system that could damage important regions of the brain. Developments in MRI like diffusion tensor imaging (DTI), a technique that tracks the diffusion of water along the brain's signal-carrying white matter tracts, have enabled researchers to study this damage directly.
For the new study, researchers compared DTI results in 59 obese adolescents and 61 healthy adolescents, ages 12 to 16 years. From DTI, the researchers derived a measure called fractional anisotropy (FA), which correlates with the condition of the brain's white matter. A reduction in FA is indicative of increasing damage in the white matter.
The results showed a reduction of FA values in the obese adolescents in regions located in the corpus callosum, a bundle of nerve fibers that connects the left and right hemispheres of the brain. Decrease of FA was also found in the middle orbitofrontal gyrus, a brain region related to emotional control and the reward circuit. None of the brain regions in obese patients had increased FA.
"Brain changes found in obese adolescents related to important regions responsible for control of appetite, emotions and cognitive functions," said study co-author Pamela Bertolazzi, a biomedical scientist and Ph.D. student from the University of São Paulo in Brazil.
This pattern of damage correlated with some inflammatory markers like leptin, a hormone made by fat cells that helps regulate energy levels and fat stores. In some obese people, the brain does not respond to leptin, causing them to keep eating despite adequate or excessive fat stores. This condition, known as leptin resistance, makes the fat cells produce even more leptin.
Worsening condition of the white matter was also associated with levels of insulin, a hormone produced in the pancreas that helps regulate blood sugar levels. Obese people often suffer from insulin resistance, a state in which the body is resistant to the effects of the hormone.
"Our maps showed a positive correlation between brain changes and hormones such as leptin and insulin," Dr. Bertolazzi said. "Furthermore, we found a positive association with inflammatory markers, which leads us to believe in a process of neuroinflammation besides insulin and leptin resistance."
Dr. Bertolazzi noted that additional studies are needed to determine if this inflammation in young people with obesity is a consequence of the structural changes in the brain.
"In the future, we would like to repeat brain MRI in these adolescents after multi-professional treatment for weight loss to assess if the brain changes are reversible or not," she added.
https://www.sciencedaily.com/releases/2019/11/191125100405.htm
Being teased about weight linked to more weight gain among children
May 30, 2019
Science Daily/NIH/Eunice Kennedy Shriver National Institute of Child Health and Human Development
Youth who said they were teased or ridiculed about their weight increased their body mass by 33 percent more each year, compared to a similar group who had not been teased, according to researchers at the National Institutes of Health. The findings appear to contradict the belief that such teasing might motivate youth to change their behavior and attempt to lose weight. The study was conducted by Natasha A. Schvey, Ph.D., of the Uniformed Services University of the Health Sciences in Bethesda, MD, and colleagues at NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development and National Institute of Diabetes and Digestive and Kidney Diseases. It appears in Pediatric Obesity.
The study involved 110 youth who were an average of 11.8 years of age when they enrolled. The participants were either overweight (defined as a body mass index above the 85th percentile) when they began the study or had two parents who were overweight or obese. At enrollment, they completed a six-item questionnaire on whether they had been teased about their weight. They then participated in annual followup visits for the next 15 years.
The researchers found that youth experiencing high levels of teasing gained an average of .20 kg (.44 lbs) per year more than those who did not. The authors theorize that weight-associated stigma may have made youths more likely to engage in unhealthy behaviors, such as binge eating and avoiding exercise. Another possible explanation is that the stress of being teased could stimulate the release of the hormone cortisol, which may lead to weight gain.
https://www.sciencedaily.com/releases/2019/05/190530101213.htm
Brain's appetite regulator disrupted in obese teens
November 30, 2017
Science Daily/Radiological Society of North America
Researchers using advanced MRI to study obese adolescents found disrupted connectivity in the complex regions of the brain involved in regulating appetite, according to a new study.
According to the Centers for Disease Control and Prevention (CDC), obesity has more than quadrupled in adolescents over the past 30 years. It is estimated that more than one-third of children and adolescents in the U.S. are overweight or obese. Obesity in adolescence is associated with a number of health risks, including cardiovascular disease and diabetes.
The study at the University of Sao Paulo in Brazil included 59 obese adolescents between the ages of 11 and 18 and 61 healthy control adolescents matched for gender, age, socio-economical classification and education level. The adolescents were classified by the World Health Organization criterion for obesity. They had no other known chronic diseases or conditions. The study participants underwent diffusion tensor imaging (DTI) of the brain to evaluate white matter integrity.
DTI is a type of MRI exam that measures functional anisotropy (FA), the microscopic motion, or anisotropy, of water molecules within and surrounding the brain's white matter fibers. Low FA values indicate greater disruption within the white matter.
"DTI is a relatively new MRI technique not widely used in clinical diagnosis," said study author Pamela Bertolazzi, a biomedical scientist and Ph.D. student in the neuroimaging laboratory at the University of Sao Paulo.
The results showed loss of white matter integrity in several brain regions in the obese patients. Compared to the healthy controls, the brains of the obese adolescents showed a decrease in FA values in areas of the brain including the amygdala, hippocampus, thalamus, cingulate gyrus, fornix, insula, putamen, orbital gyrus and bilateral hypothalamus. Several of these regions are involved in appetite regulation, impulse control, emotions and reward and pleasure in eating.
"The data reveal a pattern of involvement among brain regions that are important in the control of appetite and emotions," Bertolazzi said. "There was no region of higher FA in obese patients compared to the control group," she added.
The researchers hope that these findings will offer new tools to combat this global public health crisis.
"Childhood obesity has increased 10 to 40 percent in the last 10 years in most countries," Bertolazzi said. "If we are able to identify the brain changes associated with obesity, this DTI technique could be used to help prevent obesity and avoid the complications associated with the condition."
https://www.sciencedaily.com/releases/2017/11/171130090044.htm