Science and Medicine

Professor Michael Cowley discovered that a high-fat diet caused brain cells to become insulated from the body, rendering the cells unable to detect signals of fullness to stop eating. (Credit: Image courtesy of Monash University)

An international study has discovered the reason why some people who eat a high-fat diet remain slim, yet others pile on the weight.

The study, led in Australia by the Monash Obesity and Diabetes Institute (MODI) at Monash University, found a high-fat diet causes brain cells to become insulated from the body preventing vital signals, which tell the body to stop eating and to burn energy, from reaching the brain efficiently.

MODI director and Australian Life Scientist of the Year Professor Michael Cowley said there were two clear outcomes from the findings.

“We discovered that a high-fat diet caused brain cells to become insulated from the body, rendering the cells unable to detect signals of fullness to stop eating,” Cowley said. “Secondly, the insulation also created a further complication in that the body was unable to detect signals to increase energy use and burn off calories/kilojoules.”

The research showed that support cells in the brain developed overgrowth in a high-fat diet. This prevented the regular brain cells (the melanocortin system or POMC neurons) from connecting with other neural mechanisms, which determine appetite and energy expenditure.

Cowley said the study findings provide a critical link in addressing the obesity epidemic.

Read more: Brain Cells—Not Lack of Willpower—Determine Obesity, Study Finds

“Stress is a serious part of modern life affecting many areas of health and life,” Koren said. “This study has implications for research and for practice, as stress can be managed with lifestyle changes and psychotherapy."

Researchers at The University of Western Ontario have provided the first direct evidence, using a biological marker, to show chronic stress plays an important role in heart attacks.

Stressors such as job, marital, and financial problems have been linked to the increased risk for developing cardiovascular disease, including heart attack. But there hasn’t been a biological marker to measure chronic stress. 

Gideon Koren and Stan Van Uum developed a method to measure cortisol levels in hair, providing an accurate assessment of stress levels in the months prior to an acute event such as a heart attack. The research is published online in the journal Stress.

Cortisol is considered to be a stress hormone. Its secretion is increased during times of stress. Traditionally it’s been measured in serum, urine, and saliva, but that only shows stress at the time of measurement, not over longer periods of time. Cortisol is also captured in the hair shaft.

“Intuitively we know stress is not good for you, but it’s not easy to measure,” said Koren, who holds the Ivey Chair in Molecular Toxicology at Western’s Schulich School of Medicine & Dentistry. 

“We know that on average, hair grows one centimeter a month, and so if we take a hair sample 6 cm long, we can determine stress levels for six months by measuring the cortisol level in the hair,” he said.

Read more: Hair Shows Link Between Chronic Stress and Heart Attack