If a person has a high-fat snack or meal during a time of stress, that fat is going to be circulating in the blood for a longer period of time

Catherine Stoney, Ohio State University

These age groups were chosen so researchers could compare pre and postmenopausal women to examine the theory that reproductive hormones might affect how triglycerides are cleared from the bloodstream.

Each of the 70 underwent two 40 minute tests within a three day period.

In both tests, a solution containing triglycerides - the equivalent of about 100 calories - was administered into the volunteers' veins to mimic what would happen in a person's bloodstream hours after they ate a meal containing fat.

In one session, the volunteers rested. In the other, the volunteers were administered the triglyceride solution and were then given stressful tests including having to prepare and give a videotaped speech, a difficult word problem, drawing mirror images, and quick-fire maths tests, while their triglyceride level was monitored.

Clearing fats

The researchers found triglyceride levels declined by an average of 2.8% a minute in the stress-inducing test session, compared to a 3.2% per minute in the resting session.

In some people there were significant differences in the way they metabolised fats in the two tests, while in others the differences were quite small.

But in all cases, stress meant a person processed the fats more slowly.

In the resting session, women were found to clear triglycerides out of their bloodstream more quickly than men.

There was also no difference in how pre and post-menopausal women reacted to the tests, even when those who had been through the menopause were taking HRT, suggesting reproductive hormones do not affect how triglycerides are processed.

There was no difference in how quickly men and women cleared triglycerides during stress.

Catherine Stoney, co-author of the study and professor of psychology at Ohio State University, said: "During stress, people are not metabolising fat as rapidly and efficiently.

"If a person has a high-fat snack or meal during a time of stress, that fat is going to be circulating in the blood for a longer period of time.

"That means it may be more likely to be deposited in the arteries where it can contribute to heart disease."

Belinda Linden, medical spokesperson for the British Heart Foundation, said: "This research indicates that triglycerides may stay in the blood for longer periods of time when people are stressed.

She added: "Although it does add to our understanding of stress and triglycerides, the research has only used a small sample of people in one geographical area.

"Further large-scale randomised research is needed."

The study appears in the journal Psychophysiology.