Losing weight and VO2 Max

Well tonight at the Lansing Marathon clinic I was expressing to Owen my belief that at my age and desire to put in training hours, that my biggest weapon in gaining speed in competitive endurance events was to simply lose weight. I could spend thousands of dollars on an expensive wheel set for a triathlon...or I could lose weight. Immediately he said,
     "Well of course you're right. What two things happen when you lose weight to increase your competitiveness?" he asked me.
I didn't really have an answer but I was thinking that losing weight is good because when you don't have as much weight to cart around over 140.6 miles you'll go faster. I didn't really say that because I wasn't prepared for his question anyway. That is what I've thought of since the encounter. He answered:
     "First of all your running economy will be better", (kind've what I was getting at initially).
     "And secondly what?" He asked.
So I really didn't know. I said nothing. He said,
      "Your VO2 Max goes up. Not absolute, but relative VO2 Max."
I've actually done VO2 Max tests on my cross country teams in the past and thought about the merits of doing that kind of thing so I actually knew a little about what he was saying. I guess being a coach you don't always care about the why of things if you know they work, but it really is nice to have the why of things explained once in awhile. What it comes down to is: it's been a long time since I've had a coach and I'm looking forward to running this marathon with my daughter.