Physical activity and the prevention of type 2 diabetes mellitus - How much for how long?

From observational studies to clinical trials in a variety of populations a nd age groups, evidence is mounting in support of the hypothesis that physi cal activity plays a significant role in the prevention of type 2 diabetes mellitus. Based on the current findings, it is likely that physical activit y can reduce the risk of diabetes mellitus development. What is less clear is how much physical activity is necessary, and for how long. Obviously, we are more likely to see the anticipated physiological changes if we maximise the dose. Yet, although maximal is better from a physiologic al point of view, we 'in the trenches' have also recognised the fact that a sedentary individual will most likely not continue to undergo a high inten sity activity exercise regimen. In contrast, evidence is mounting regarding long term compliance to moderate levels of activity, which appear to be ea sier to adopt in one's lifestyle and are less likely to result in injury. M ore importantly, there appear to be beneficial changes in insulin sensitivi ty and glucose tolerance in the sedentary individual who incorporates moder ate levels of activity such as walking into the their lifestyle, although t he onset of beneficial metabolic changes appear to occur much more slowly a nd less dramatically than what occurs with a high intensity regimen. Even if activity is shown to be beneficial, we are faced with the challenge of reaching the sedentary individuals who would most likely benefit from a n increase in physical activity in the first place. This task is a difficul t one because of the difficulty in quantifying the sum total of an entire d ay's worth of movement, rather than that of a few relatively higher intensi ty leisure activities. What is needed is a measure or combination of measur es of physical activity that are simple to use, relatively inexpensive, and adequately capture the subtle changes in physical activity through the day that we are encouraging. It is unlikely that the protective nature of a physically active lifestyle in preventing diabetes mellitus will have a lasting impact once a switch to a sedentary way of life is made. Therefore, from a public health viewpoint , long term commitments to increased activity are required. This is the ult imate challenge.