Researchers at Cambridge University are launching the second phase of a unique study of diabetes, this time investigating how physical inactivity affects the onset of the disease.
More than 1,100 people who thought they were free of diabetes took part in the first phase of the Isle of Ely diabetes project, organised by the university's departments of community medicine and clinical biochemistry. Fifty-one volunteers, almost 5 per cent, were found to have hitherto undiagnosed diabetes, while 188, almost 17 per cent, were found to have impaired glucose tolerance, a condition which may precede the disease.
Exercise is known to be beneficial for people with diabetes, and there is some research evidence that increased physical activity may reduce the risk of people with impaired glucose tolerance developing the disease, says Nick Wareham of Cambridge's community medicine department.
But the epidemiological studies that exist do not make clear whether the risk comes from not exercising vigorously or from having a generally low level of exercise.
"The public health implications are different. Should we be telling people to have periods of vigorous activity, or just increase their background level of activity? We think the two are not the same," says Dr Wareham.
The Cambridge team has now joined forces with the Medical Research Council's Dunn Clinical Nutrition Centre, who have developed a method of assessing the volunteers' level and pattern of physical activity. Each volunteer's heart rate is plotted against their oxygen consumption while they are gently cycling on a stationary bicycle, and they then wear a small monitor which stores records of minute-by-minute heart rates over the next few days.
Research comparing this with the most precise techniques for measuring energy expenditure have shown this method to be highly accurate, and it is the first study to use it on a large scale in adults.
The study should help the researchers address the question of whether the beneficial effects of periods of rigorous exercise are different from the benefit derived from more low-level activity, says Dr Wareham.
"This sort of ongoing study can provide important information about the cause of disease, as it's possible to be certain that risk factors measured at the start of the study predate the development of diabetes. We also hope to discover ways to predict who is at increased risk of developing the disease in the future."