In a recent popular running magazine there was an article about the affect of weight on your running times. The logic goes like this since VO2max is a function of body weight (your ability to process oxygen) if you lose weight you go faster due to an increase in your VO2max. The half truth is that yes, decreases in body weight do indeed increase VO2max (it’s part of the equation). The half lie is that VO2max is not a good indicator of running performance and in fact there are many instances of higher VO2max individuals who are beaten by those with lower VO2max readings. Why? Because VO2max is like enlarging your tank of gas. Nice, but if you don’t use it efficiently it doesn’t matter. The false analogy is that your VO2max is like the engine of your car. It is not. Your engine is more like the neuro-muscular and chemical reactions that cause the contractions of muscles. I don’t want to mislead you as this article I reference does. It is indeed true that improving your VO2max is one factor to look at in improving performance.
Running miles does positively affect your VO2max. VO2max can be improved by about 16% going from zero to 25 miles per week and another 16% moving from 25 to 50 miles per week but only 3% to move from 50 to 70 miles per week and perhaps not at all according to the research after 70 miles per week! This does not however mean that you will improve your race times by those respective mileage increases and associated VO2max improvements.
The more valid and reliable variable is your vVO2max – the velocity (pace) at which you reach your VO2max. This pace is far more predictive of your race capabilities (5k through marathon and beyond) than is VO2max. The way to improve vVo2max is through high quality workouts. In fact in the article there is a brief reference to the effect that less weight will allow you to run further and faster workouts so you will race faster. There is indeed the rub. It is not the weight loss (and subsequent improvement in VO2max) directly that lets you go faster. It is only if you deliberately run progressviely faster paces in your workouts that is turning the trick. Continuing to run at your old paces at a lighter weight with lofty VO2max readings will not make you faster.
So be careful in applying these theoretical formulas in losing weight and getting faster.