People with metabolic syndrome display a combination of at least three symptoms from obesity, high blood sugar, raised levels of triglycerides (a type of fatty acid found in the blood) and low levels of HDL, a so-called "good cholesterol".

The researchers said they were encouraged that the biological effects of stress were thought to be reversible if men reduced their risk factors, such as losing weight or lowering their blood pressure.

Dr Eric Brunner, who led the research, said: "This study provides biological and therefore more objective evidence than ever before of the link between stress and metabolic syndrome." Although this is not concrete proof that stress causes metabolic syndrome or indeed heart disease, we are certainly closer to proving it."

Professor Sir Charles George, medical director at the British Heart Foundation, said: "The link between stress and heart disease is still unclear but this study is significant as it helps us to understand more about the relationship between the conditions.