Scientists still argue about the most important contributing factor to the ever increasing obesity epidemic in the Western World: Is it bad dietary habits or our sedentary lifestyle - honestly, I don't care... you got to work on both if you want to stay healthy.
The results of a recent study published by scientists from the Toho University Sakura Medical Center (Yamaguchi. 2010) do yet underline the importance of exercise (and I mean exercise, as in sweating and panting, not just walking to your car!) in the "health equation", i.e. "diet + exercise = health". The scientists had their 19 obese type 2 diabetics either keep their sedentary lifestyle or performed 2× 30-min bouts of exercise (treadmill walking) everyday in the morning and evening during the 4-week study period. What is of particular importance is that the exercise intensity was determined by pretesting the exercise capacity of each participant, so that all patients exercised at their individual anaerobic threshold. The results of this regimen (cf. table 1) were quite remarkable:
Although this is just speculation on my part, I think it is questionable whether walking for more than 30 minutes, but at a lower intensity would have provided similar results. Or in other words: If the key is to trigger metabolic changes (via natural hormonal pathways) intensity (not overexerting oneself, though) is key.