In new study from The Ohio State University (OSU), researchers found that women who experienced stress in the previous 24 hours burned 104 fewer calories than non-stressed women in the time after eating a high-fat meal—which adds up to the equivalent of 11 pounds gained annually.
"We figured stress and depression alter so much in our lives, physiologically, but no one has really looked at metabolism, so it was an interesting opportunity to see how they might affect the metabolic process," Jan Kiecolt-Glaser, a professor of psychiatry and psychology at OSU, told FoxNews.com.
For the study, 58 women with an average age of 53 were given three standardized meals the previous day and then were instructed to fast for 12 hours before reporting for their study visit. Then, on the day of the study, the women were fed a meal consisting of eggs, turkey sausage, biscuits and gravy. The meal, which was 60% fat, was the equivalent of a fast food meal of a loaded two-patty hamburger and French fries. Each of the participants went through with the experiment two times.
"It's really the equivalent of grabbing a fast food meal," Kiecolt-Glaser, also director of the Institute for Behavioral Medicine at OSU, said. "When people are stressed, depressed and in a hurry, we don't usually reach for broccoli unless it has a lot of hollandaise on it."
After the women ate their meals, they sat in semi-reclined beds for the following seven hours, while researchers monitored their resting metabolic rate, or resting energy expenditure, which had also been measured prior to eating. Resting energy expenditure, when the body is not in motion, accounts for 65 to 75% of the calories the body burns in a day. Additionally, ten percent of a person's daily calories are burned by digesting food. Daily activities, not including heavy exercise, account for another 15 to 25% of daily calorie burn, Kiecolt-Glaser said.
"Resting energy expenditure is a really big deal because it’s a large portion of our daily energy expenditure," she said.
Before each round of the experiment, study participants also filled out a daily inventory of stressful events (DISE) test, which objectively measures stress levels. The most reported issues were interpersonal problems, such as trouble with children, work-related pressures or disagreements with spouses.
"These are things that tend to be the most stressful for people," Kiecolt-Glaser said. "And I think people are still thinking about things and remembering them and still dealing with them [the next day.]"
The DISE test revealed that 31 participants reported experiencing at least one stressor before one round of the experiment, 21 participants reported experiencing at least one stressor before both rounds and six women reported no stressors.
Analyzing the DISE results and resting metabolic rate measures, researchers found that women who had at least one stressor in the previous 24 hours burned 104 fewer calories than women who reported no stressors the day before. They also found that women who had reported stressors showed a higher rise in insulin levels following the meal. Previous research suggests that stress and depression may promote insulin resistance and the data from this experiment shows one mechanism through which that could occur, researchers said.
Kiecolt-Glaser noted that while it's likely that most people don't experience a stressor every day, the potential for stressors to cause weight gain is still significant.
"If you experience a stressor one-third of the time, that would still be between 3 and 4 pounds gained. It could still over time contribute if you're eating a high-fat meal," she said.
During the study, researchers also analyzed the metabolic impact of a high-fat meal made with saturated fat, compared to one made with sunflower oil, which contains monounsaturated fat. Looking at metabolic outcomes and inflammatory consequences, they found little difference between the two types of fat.
Researchers concluded that their findings should offer motivation for people to keep healthful foods nearby at all times.
"When you're feeling stressed and depressed, really keep an eye on what you might be reaching for as your first choice. Keep healthy snacks in the fridge that you can grab easily because those are the times you are less likely to want to prepare something," Kiecolt-Glaser said. "People can't easily avoid stress in their lives...but it's recognizing it and trying to change behavior around it."
The researched was published in Biological Psychiatry.
