Stress hormones and obesity
Most people when stressed overeat. Only 15 per cent of people lose their appetite. How and why stress triggers this behaviour, and obesity, has remained a mystery until now.
For the first time, Monash researchers from the School of Biomedical Sciences have shown a link between the level of the stress hormone cortisol and behaviour that may be associated with weight gain. The scientists have teased out who is predetermined to be obese and how stress triggers cause overeating and reduced calorie burning.
Therefore, doctors may be able to identify at-risk people before they put on excess weight and help them manage their stress and also prevent obesity.
Previously, the research team have shown that people who have a high cortisol response are more likely to become obese than individuals with a low cortisol response. These high responding individuals may also struggle to lose that weight.
In work published in the journal Psychoneuroendocrinology, the researchers have now identified other characteristics of ‘high cortisol responders’. Using a sheep model, Dr Belinda Henry, from the Department of Physiology, has found that these high responders (about 10 per cent of the population) respond to stress differently to low responders, which may explain why they are prone to becoming obese.
Low cortisol responders, who tend to lose their appetites and reduce their food intake in response to stress, show an increase in energy expenditure.
Meanwhile, high responders do not reduce food intake in response to metabolic and psychological stressors.
Currently, the only effective treatment for morbid obesity is surgery as medications to reduce food intake are ineffective. However, targeting energy expenditure may be another way to address the escalating problem, and this is where the group have identified individual differences.
According to Dr Henry, preliminary data indicate that the level of cortisol response is determined by our genes. Although this work was carried out in sheep, it is broadly applicable across species, including humans. The research team is now embarking on a human study to determine whether they can identify who is susceptible to becoming obese.
“If we can predict who is more likely to end up obese – particularly in response to stressful events – then we can intervene early to prevent this disease from occurring as well as other complications associated with weight gain such as heart disease, cancer and diabetes,” Dr Henry said.
The research team are now collaborating with Dr Kevin Lee, who is recruiting 40 volunteers to take part in a clinical trial at Monash University’s BASE facility, to determine whether low and high cortisol responders have different metabolic, immune and behavioural responses to stress.
“The most exciting thing about stress responsiveness as revealed by the stress hormone cortisol is that it ties together complex links between metabolism and coping behaviour to stress which many patients have known to be intuitively true,” he said.
“It’s nice to see how basic research can also inform our next move in our battle against the obesity epidemic which costs Australia in terms of its complications like diabetes, heart disease and cancer, over $58 billion a year.”