Run faster for shorter period

Question
I have been running on my treadmill three times a week for forty five minutes,to lose weight.I go at about 4mph.
Lately I have less time to run.If I run faster,say 5mph for twenty to thirty minutes,will I get the same benefits,or is time as opposed to speed the factor for losing weight?  

Answer
Hi Brian
Time is allways better, but if you are short on time,increasing the speed will keep you in the game.The one big caveat would be to take a closer look at your diet and get truly focused which would fill in the gaps.

To your continued success

John