Comfort eating increases stress.
Many people seek solace in unhealthy snacks during anxious times but they actually impede the body's recovery from the impact of tension.
Eating food high in fat prior to moments of mental stress reduces oxygen getting to the brain and also increases the risk of cardiovascular disease.
A team of experts took a group of young healthy adults and provided them with two butter croissants for breakfast. They were then asked to do mental maths, increasing in speed, and were alerted when they answered incorrectly.
The boffins found that consuming fatty foods when mentally stressed reduces vascular function by 1.74 per cent.
Rosalind Baynham, of the University of Birmingham, said: "Stress is something that we all need to deal with.
"So, next time you are in a big meeting, or in a job interview try and resist the free biscuits and go for some berries. You might find you feel more relaxed."