Not if they are fed in moderation. The same applies to all carbohydrates, which are converted into glucose by the horse's pancreas before being utilised by the body. However, when glucose is already present in the blood, the body will convert it into glycogen for storage within the liver and muscles. A horse with an insulin resistant condition will need to be fed in a way that will enable the conversion of glucose into glycogen, without the presence of excessive amounts of glucose in the blood stream. Carrots are therefore a good carbohydrate source for such horses. As well as having a high fibre content, carrots also contain Vitamin C and Beta-carotene, which are beneficial to a horse's health.