Eating a fatty meal after a stressful day can slow a woman’s metabolism and help her gain weight, research has shown.
Women who experienced one or more stressful events burned significantly fewer calories than those who did not, scientists found.
The difference was big enough to pile on almost five extra kilograms over the course of a year, prompting a warning not to resort to unhealthy comfort food at times of stress.
Stressed women had higher levels of insulin, which contributes to fat storage. Their fat was also less likely to be oxidised − converted into a form that can be used as fuel.
US lead scientist Jan Kiecolt-Glaser, from Ohio State University, said: “This means that, over time, stressors could lead to weight gain.
“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 scientists questioned 58 middle-aged women about how stressed they were the previous day before giving them a meal containing 930 calories and 60 grams of fat.
On average, those women who reported experiencing one or more stressful events burned 104 fewer calories than non-stressed women in the seven hours following the meal.
The double whammy of past depression, as well as daily stressors, was a really bad combination
Over the course of a year, slowing metabolism by this much could result in weight gain of almost five kilograms, said the researchers whose findings appear in the journal Biological Psychiatry.
Stressful events reported by the women included arguments with work colleagues or spouses, disagreements with friends, trouble with children or job-related pressures. Only six women claimed to be completely stress-free.
The research meal comprised eggs, turkey sausage, biscuits and gravy − roughly the calorie and fat equivalent of a double-layer hamburger and French fries.
“This is not an extraordinary meal compared to what many of us would grab when we’re in a hurry and out getting some food,” said Kiecolt-Glaser, director of the Institute for Behavioural Medicine.
A surprising finding was that giving some women meals containing saturated fat and others healthier sunflower oil made no difference.
Ohio State nutritionist and co-author Martha Belury said: “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.”
Blood samples showed that in stressed women, insulin levels spiked soon after the high-fat meal was eaten. It then decreased until it roughly matched those of unstressed women after 90 minutes.
A history of depression alone did not affect metabolic rate. But depression combined with stressful events led to a steeper rise in triglyceride blood fats − a risk factor for heart disease − after the meal.
“The double whammy of past depression as well as daily stressors was a really bad combination,” said Kiecolt-Glaser.
The scientists are not sure men would experience the same pattern, since they tend to have more muscle which affects their metabolic rate.
Belury advised women to make an effort to avoid comfort food after getting stressed.