Effect of weight loss on speed
The effect of a change of weight can be calculated here.
The calculation assumes that everything else is held constant – so that the body’s capacity to turn oxygen into energy is otherwise unaffected. This means that VO2 max would change in direct proportion to the percentage change in weight. The predicted performances are derived by simply calculating the predicted race performance at the new VO2 max.
In real life, however, everything else would not be constant. A reduction in weight might be accompanied by:
- a higher background level of training;
- lower muscle mass;
- reduced immunity;
- reduced glycogen stores;
- lower levels of hydration
All but the first of these would be expected to lead to a deterioration in athletic performance. These changes would have to be offset against the direct benefits of the weight loss.