change in horse weight

Question
hello sir. may i know why does change in horse body weight matters a lot in thoroughbred horse racing?

sir, do fat thoroughbred horses run badly when compared to the light weight ones?

Answer
Each horse will have their own ideal performance weight by design. A fat horse may be fit, but may be more likely to injure himself with the unnecessary weight. Some horses may appear skinny with ribs showing, but may perform at their best this way. A horse can lose 10% of its body weight in one race if conditions are harsh and the horse puts out maximum effort. Keep track of each horse's pre and post race condition so you can track his rate of recovery.  You want to keep enough fat on your horse for proper thermo-regulation and metabolic balance. A properly trained and fed horse should hold a good weight under normal conditions.