Changes

It seems intuitive that excess body fat makes a runner slower. Body fat does not help you run, and adds weight that must be carried. The science seems to support this, as aerobic performance is based on how much oxygen you can use, and it is primarily [[Muscle|muscle]] that is using that oxygen, not fat. But how much difference does body fat make? There's a simple answer based on the weight of fat, but the reality might be more complex.

= The Simple Answer =

The first assumption is that [[Jack Daniels Running Formula]] [[VDOT]] is close enough to [[VO2max|V̇O₂max]] to be useful. [[VO2max|V̇O₂max]] is how much oxygen you can use per minute per Kg of body weight. The second assumption is that you can lose body fat without losing any muscle. If [[VDOT]] is how much oxygen you use per Kg body weight, then you can multiply [[VDOT]] by body weight to work out the total max oxygen use. If you lose body fat only, then the total max oxygen should stay the same. You can then divide the total max oxygen use by the new body weight to get a new [[VDOT]]. This is worked out in my [[Running Calculator]], and losing 5% of body weight will give a roughly 5% improvement in performance.