thanks for the replies all. During my last checkup my pcp basically said all I need to do is lose weight. Otherwise I am fairly healthy.
I guess what I am trying to get a better understanding of is that some people able to handle being overweight more than others. Like I say I've seen guys at the gym who are rounder and outweigh me by a ton, but can still out run me and have more stamina than I do(even when I was running my very slow paced 15 miles a week).
It just makes me so frustrated that for all the hard work I put into my conditioning/weight loss I am still very constrained on the court by not being able to give it my all due to having to conserve energy.
I guess I will wait and see how I am when I get to my weight goal.