May 02, 2014 04:10 AM EDT By Staff Reporter, UniversityHerald Reporter

People who are highly stressed and eat a diet rich in fat and sugar are at an increased risk of developing health problems than low stressed people with a similar diet chart, according to a University of California - San Francisco study.

"Chronic stress can play an important role in influencing biology, and it's critical to understand the exact pathways through which it works," Kirstin Aschbacher, PhD, an assistant professor in the UCSF Department of Psychiatry and lead author, said in a statement. "Many people think a calorie is a calorie, but this study suggests that two women who eat the same thing could have different metabolic responses based on their level of stress."

"There appears to be a stress pathway that works through diet - for example, it could be similar to what we see in animals, where fat cells grow faster in response to junk food when the body is chronically stressed."

People with different metabolism rates respond differently to stress factors. There are certain metabolic traits that can indicate risk for disease like high fasting blood sugar, high triglyceride level, a large waistline and low HDL cholesterol level.

Previous studies showed evidence of stress-junk food pathway in rodents and primates. This is the first study to find proof of similar pathway in chronically stressed humans.

"We can see this relationship exists by simply measuring stress and dietary intake, and looking inside at metabolic health," said senior author Elissa Epel. "Diet appears to be a critical variable that can either amplify or protect against the metabolic effects of stress, but we still don't know the details of how much it takes. It will be helpful to see what happens in our next study, when we have high stress people eat a high sugar diet for a couple weeks."

For the study, the researchers surveyed 61 disease-free women; 33 chronically stressed and 28 low stressed women for a year. The participants reported their intake of sugar and fat foods.

The researchers assessed key biological markers linked to heightened metabolic risk. They measured participants' waistlines, fat content, abdominal fat deposits (using ultrasound scans), stress hormones and oxidative damage to lipids and cell RNA (using blood test) -  a marker that has predicted higher death rates from diabetes. The researchers also tested participants' insulin resistance, one of the important factors for obesity and diabetes.

Aschbacher said that chronic stress participants who ate food rich in fat and sugar in higher quantities were found to have a larger waistline, more truncal fat, higher oxidative damage, and more insulin resistance.

These participants had a diet similar to low stressed women. However, they had higher levels of peripheral Neuropeptide Y (NPY) - a stress-related biomarker. Studies conducted on animals found that stress leads to higher production of peripheral NPY, which in combination with junk food generates larger abdominal fat cells. These cells are more likely to cause metabolic dysregulation.

Aschbacher said that treatments have not yet been developed for chronic stress. Further studies will be conducted to find out whether enhanced stress resilience could lower the risk of metabolic syndrome, obesity or diabetes.

The finding is published in the journal Psychoneuroendocrinology.

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