The Ohio State University 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 their metabolic rate, how long it took the women to burn calories and fat, and took measures of blood sugar, triglycerides, insulin and the stress hormone cortisol.
On average, the women in the study who reported one or more stressors during the previous 24 hours burned 104 fewer calories than non-stressed women in the seven hours after eating the high-fat meal, a difference that could result in weight gain of almost 11 pounds in one year.
It was found that stressed women also had higher levels of insulin, which contributes to the storage of fat, and less fat oxidation.
Lead author of the study, Jan Kiecolt-Glaser said that the data shows people were more likely to eat the wrong foods when stressed, which is when weight gain becomes more likely because there are fewer calories burning.
The study was conducted in 58 women, average age 53, and included two admissions to Ohio State's Clinical Research Center for daylong analyses. To regulate their food intake for 24 hours before eating the high-fat meal, researchers supplied the 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 participants 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.
Participants were required to eat the meal consisting of eggs, turkey sausage, biscuits and gravy 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.
The stressors' effects of increasing insulin had a time element: Insulin spiked soon after the high-fat meal was consumed and then decreased to roughly match insulin levels in non-stressed women after another 90 minutes.
Kiecolt-Glaser said that past depression as well as daily stressors was a really bad combination as they that triglycerides peaked the highest in women who had stress the day before and a history of depression.
The research is published in the journal Biological Psychiatry.