Slaving away in the gym might just be a waste of time for many, for one in every six persons doesn't get any benefit from it in shedding weight or toning the body. The receptivity to exercise actually lies in our genes, says Louisiana State University study.
As part of the study Dr Claude Bouchard and colleagues examined the differing effects on 742 sedentary people from a 20-week exercise programme, in which the intensity was gradually increased.
The researchers measured ability to process oxygen, ability to pump blood round the body, pulse rate, blood pressure and insulin resistance in the subjects.
The study found that 10-15 per cent of volunteers were 'non-responders' to aerobic exercise.
In some volunteers the peak rate at which their muscles could process oxygen increased by up to 40 per cent, while in others there this key measure of cardiovascular fitness, known as 'VO2 max' did not improve at all.
"Some people simply respond better to exercise. They have lower heart rates, lower cholesterol, lower blood pressure, better response to insulin and a host of other positive responses. Others who exercise the same amount simply don't get all the benefits, and it appears to be in the genes," the Telegraph quoted the researchers, as saying.
The researchers are now trying to identify which genes are responsible for receptiveness to exercise.