It is known that horses are typically more insulin sensitive than ponies , and correlations have been shown between morphometry and insulin sensitivity . The aim oft his study was to quantify the glucose and insulin responses to the same meal in horses with moderate body condition scores(BCS) as well as obese ponies, thereby using both disparate breeds and morphometry.
Tinworth, K. D., Raidal, S. L., Harris, P. A., Sillence, M. N., & Noble, G. K. (2011). Comparing glycaemic and insulinaemic responses of ponies and horses to dietary glucose. Journal of Equine Veterinary Science, 31(5), 301. https://doi.org/10.1016/j.jevs.2011.03.129