Researchers from the Emory University School of Medicine in Georgia have discovered that regular exercise protects the body by increasing the number of cholesterol-fighting molecules.

But experiments on students who had just started doing exercise classes showed short bursts of activity either had no effect on cholesterol or increased it, they said.

This will be bad news for the many who adopt a binge and starve approach to exercise.

Vaccine

Writing in the Journal of the American Heart Association, Sampath Parthasarathy says regular exercise acts like a vaccine on the immune system, reducing heart disease.

But there is some good cheer for those who convince themselves that doing the odd bit of running, aerobics or football during the summer allows them to spend most of the rest of the year on the sofa, watching TV.