Maybe this will help. when you measure VO2max it is expressed in two different ways (1) liters or milliliters of Oxygen consumed per minute; this is your absolute VO2max. (2) divide you absolute max (in ml per minute)by your body mass (in kilograms) and you get your relative VO2max (in milliliters per minute per kilogram). So, there is one way to increase your absolute VO2max -- conditioning -- and two ways to increase your relative max -- by increasing your absolute max or by reducing your body mass. Problem with just reducing your body mass (as the way you choose for increasing relative max) is that any loss in muscle mass (of those muscles used in running, not muscles in your arms, for example) can result in a loss of absolute max, so you are now dividing a lower absolute value by a lower mass and may not go up in relative max (in fact may go down). For example, if your absolute max is 4000ml/min and you weigh 60 kg, then your relative max is 66.7. If you drop body mass to 56 kg, but some of that loss is useful muscle, resulting in a drop in absolute max to 3640, then relative max becomes 3640/56, which gives you a relative max of 65, worse than the 66.7 you had before the weight loss. On the other hand, if all your loss in body mass was unnecessary body fat, then your absolute value of 4000 is divided by 56 and that gives you a relative max of 71.4 ml per minute per kg, which will certainly lead to better performance