New research published in Biological Psychiatry, suggests that stressful events may predispose women to slow their metabolism in response to a high fat meal, which could in turn lead to long term weight gain.
The findings come after researchers from the USA questioned participants about the previous day's stressors before giving them a meal consisting of 930 calories and 60 grams of fat. The team then measured their metabolic rate and took measures of blood sugar, triglycerides, insulin and the stress hormone cortisol.
On average, women 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, said the team.
Stressed women were also found to have higher levels of insulin – something the team noted would contribute to the storage of fat, and reduce fat burning.
"This means that, over time, stressors could lead to weight gain," said Jan Kiecolt-Glaser, professor of psychiatry and psychology at 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."
Previous research also has shown that people who experience stress and other mood disruptions are at higher risk of becoming overweight or obese. The new study may shed light on at least one mechanism behind that connection, said the researchers.
The researchers are reluctant to extend these findings to men because men tend to have more muscle than women, which would affect their metabolic rate, added Belury.
The randomised study was conducted in 58 women with an average age 53. 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 analysis, 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.
The women were then given a test (high sat fat) or control meal (high in healthier fats). After the meal, metabolic rate was tested for 20 minutes of every hour for the next seven hours.
"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 their energy expenditure," revealed Professor Martha Belury, a co-author of the study.
“The participants burned fewer calories over the seven hours after the meal when they had a stressor in their life the day before the meal,” said Belury.
Researchers also took multiple blood samples, which allowed the team to follow metabolic markers throughout the day.
From this, the team found that 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.
"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."
But the findings do offer one more motivation to keep healthful foods nearby.
"We know we can't always avoid stressors in our life, but one thing we can do to prepare for that is to have healthy food choices in our refrigerators and cabinets so that when those stressors come up, we can reach for something healthy rather than going to a very convenient but high-fat choice," Belury concluded.
Source: Biological Psychiatry
Published online ahead of print, doi: 10.1016/j.biopsych.2014.05.018
“Daily Stressors, Past Depression, and Metabolic Responses to High-Fat Meals: A Novel Path to Obesity”
Authors: Janice K. Kiecolt-Glaser, Diane L. Habash, et al