People who are under stress feel overwhelmed, worried, or run-down. It is true that stress can be beneficial at times, producing a boost that provides the drive and energy to help people get through situations like exams or work deadlines.

But chronic stress, stress that happens day in, day out and is not under our control, can have negative effects on our immune, cardiovascular, endocrine and central nervous systems.

And you can now add a tendency to belly fat to the list of negative effects stress has on our bodies.

It's not fair, but if a person whose life involves the daily stress of caring for someone who is ill or coping with the pressures of poverty eats a burger and fries or bowl of ice cream, he or she is likely to have more body fat and be in worse shape metabolically than someone eating the same foods who is not so stressed, according to a new study.

In women who were stressed, higher sugar and fat consumption was linked to a larger waist, and greater insulin resistance.

The study is the first to show in humans what’s been shown in rodents many times before — that stress can wreak havoc on the metabolism, particularly when carbohydrates and fats are consumed.

Metabolic syndrome is a group of metabolic changes that are linked to risk of heart attack and diabetes: Being overweight or obese (especially with fat around the mid-section), and having high cholesterol, high blood pressure, and high blood sugar are some of the key symptoms.

Researchers at the University of California at San Francisco decided to track how chronic stress might affect metabolism. They followed 61 women for a year — half of the women were taking care of a spouse or parent with dementia — a major source of chronic stress. The other half of the women didn’t have any major stressors in their lives.

The stressed and (relatively) unstressed women recorded how often they ate high-fat or high-sugar foods. At the end of the year, the researchers measured the women’s body fat, including where it was distributed, along with several biomarkers in the women’s blood.

In women who were stressed, higher sugar and fat consumption was linked to a larger waist, more of the damage oxidative stress can do, and greater insulin resistance. These women also had higher levels of a stress-related biomarker called peripheral neuropeptide Y (NPY). But the connection between sugar and fat consumption and metabolic changes wasn’t found in women who were not under stress.

“Chronic stress can play an important role in influencing biology, and it's critical to understand the exact pathways through which it works,” said author Kirstin Aschbacher in a news release. “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.”

Animal studies have shown that fat cells grow faster when animals are stressed and fed junk food, and a similar mechanisms may be going on in us humans, she added.

Given the amount of stress that so many people are under these days — job losses, economic pressures, divorce, caring for sick parents — the results of the study are a little disheartening. The upside is that doctors and researchers are finally beginning to understand and acknowledge the impact stress has on the body.

“The medical community is starting to appreciate how important chronic stress is in promoting and worsening early disease processes,” said Aschbacher. “But there are no guidelines for ‘treating’ chronic stress.”

That may be true, but we are learning more about how to manage stress, and the research shows that there are a number of effective ways. Talk therapy, exercise, medication, yoga and meditation all help manage anxiety and depression; it may be just a matter of figuring out what works best for you.

We may not be able to make our stress disappear, but we can figure out ways to cope with it better, so that it may have less of an impact in the long run.

The study is published in Psychoneuroendocrinology.