The science behind why some people get fitter than others.

Not everyone who exercises achieves the same gains in fitness or equal health benefits. Researchers from Japan believe they have a possible answer. They have found a liver protein called selenoprotein P that is released into the blood of people who fail to respond to exercise.

Selenoprotein P works by limiting glucose (sugar) transport into muscles. This might help explain why up to 20 percent of people with type 2 diabetes (adult-onset diabetes) have little or no improvement in blood sugar control with regular exercise.

There are currently no tests for selenoprotein P levels in the blood. So it’s not yet possible to determine who will benefit the least from exercise. Despite this, the odds remain that exercise works for most people. If not for fitness and blood glucose control, then there are the many emotional and brain benefits of regularly exercising.

Professor David Cameron-Smith is a regular Fit Planet contributor. A transplanted Australian living in New Zealand, he obtained a PhD in nutritional biochemistry from Deakin University, and undertook postdoctoral training at the Royal Prince Alfred Hospital, Sydney. His research interests include the importance of nutrition in the maintenance of optimal health in an ageing population, and the impact of nutrition in regulating the function of muscles.