Googled this article on stretching:
Feb. 28: New Study Finds That Static Streching Pre-Race Diminishes Performance | Peak Performance
"With stretching, they covered an average of 5.8 km in the last 30 minutes. Without stretching, they ran 6.0 km, an increase of 200 meters or about 3.4 percent. Eight of the 10 runners performed better without stretching; one performed better with stretching; and one performed essentially the same under both conditions. On average, the stretchers hit a max heart rate 5 beats per minute higher than the non-stretchers in the final 30 minutes. In other words, the stretchers were working harder but covering less distance.
In another interesting comparison, Panton and colleagues measured the calorie-burn of the runners during the first "easy" 30 minutes of the treadmill test. In this case, the stretchers burned more calories than the non-stretchers. In other words, the stretching routine seemed to make them less efficient."
Lower performance for distant running, but seems a bit negligible for those looking to lose weight. In fact, if stretching before a workout makes the body burn more calories, that's a good thing for people looking to lose weight.
Besides, I always thought the point of stretching was to reduce the chance of injury. So I googled that and found this:
Does Stretching Prevent Injuries? Advice from Runner's World
Which says that stretching before exercise is most likely to cause injury than prevent it.....
So yeah....