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Does High Fat + Stress Slow Metabolism?

by Emily Caldwell on Jul 24, 2014

Fitness pros: You know that some clients respond to stress by eating. Now a new study has found that experiencing one or more stressful events the day before eating a single high-fat meal can slow women's metabolism, potentially contributing to weight gain.

Researchers questioned study participants about the previous day’s stressors before giving them a meal consisting of 930 calories and 60 grams of fat. The scientists then measured the women's metabolic rate—how long it took them to burn calories and fat—and took measures of blood sugar, triglycerides, insulin and the stress hormone cortisol.

On average, in the 7 hours after eating the high-fat meal the women who reported one or more stressors during the previous 24 hours burned 104 fewer calories than the nonstressed women—a difference that could result in weight gain of almost 11 pounds in 1 year.

The stressed women also had higher levels of insulin, which contributes to the storage of fat, and less fat oxidation (i.e., conversion of large fat molecules into smaller molecules that can be used as fuel). Fat that is not burned is stored.

“This means that, over time, stressors could lead to weight gain,” said Jan Kiecolt-Glaser, professor of psychiatry and psychology at The Ohio State University and lead author of the study. “We know from other data that we’re more likely to eat the wrong foods when we’re stressed, and our data say that when we eat the wrong foods, weight gain becomes more likely because we are burning fewer calories.”

The study, published in the August 1 issue of Biological Psychiatry, was conducted with 58 women, average age 53, and included two admissions to Ohio State’s Clinical Research Center for daylong analyses. To regulate food intake for 24 hours before the high-fat meal, researchers supplied participants with three standardized meals on the previous day and instructed them to fast for 12 hours before reporting for their study visit.

On the day of admission, the women completed several questionnaires to assess their depressive symptoms and physical activity and were interviewed about stressful events on the prior day. Thirty-one women reported at least one prior-day stressor on one visit, and 21 reported stressors at both visits. Six women reported no stressors.

Most of the reported stressors were interpersonal in nature: arguments with coworkers or spouses, disagreements with friends, trouble with children or work-related pressures.

The research meal consisted of eggs, turkey sausage, biscuits and gravy—roughly equivalent in calories and fat to a loaded two-patty hamburger and French fries at a fast-food restaurant. Participants were required to eat the entire meal within 20 minutes.

The control for comparison in this randomized trial was that one meal contained saturated fat and another was high in a different kind of fat: sunflower oil containing monounsaturated fat, which is associated with a variety of health benefits.

“We suspected that the saturated fat would have a worse impact on metabolism in women, but in our findings, both high-fat meals consistently showed the same results in terms of how stressors could affect [the women’s] energy expenditure,” said Martha Belury, professor of human nutrition at Ohio State and a co-author of the study.

Before the meal, participants rested for 30 minutes, and their energy expenditure—or calories burned by converting food to energy—was tested during that time. After the meal, their metabolic rate was tested for 20 minutes of every hour for the next 7 hours. Researchers obtained this data by using equipment that measured inhaled and exhaled airflow of oxygen and carbon dioxide.

“By measuring the gas exchange, we can determine their metabolic rate: how much energy their body needs during the time being measured,” Belury said. “The participants burned fewer calories over the 7 hours after the meal when they had a stressor in their life the day before the meal.”

The insulin increase triggered by the stressors lasted for a limited time: Insulin spiked soon after the high-fat meal was consumed and then decreased to roughly match insulin levels in nonstressed women after another 90 minutes.

A history of depression alone did not affect metabolic rate, but depression combined with previous stressors led to a steeper immediate rise in triglycerides after the meal.

“With depression, we found there was an additional layer. In women who had stress the day before and a history of depression, triglycerides after the meal peaked the highest,” Kiecolt-Glaser said. “The double whammy of past depression as well as daily stressors was a really bad combination.”

While your clients can’t always avoid stressors in their lives, what can they do? “Prepare for them by having healthy food choices in their refrigerators and cabinets so that when those stressors come up, they can reach for something healthy rather than going to a very convenient but high-fat choice,” Belury said.

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About the Author

Emily Caldwell

Emily Caldwell IDEA Author/Presenter