Researchers suggest 54% of horses in the U.S. are overweight or obese, putting them at a higher risk of developing other health problems, such as metabolic issues and joint pain. However, horses might become underweight due to gastrointestinal problems, such as gastric ulcers, or chronic health challenges. Regardless of whether a horse is under- or overweight, the underlying cause is usually an imbalance between the supply of energy the horse receives and the energy he expends. The first step in managing your horse’s weight is to determine his body condition score and work with an equine nutritionist to develop a nutrition plan to meet his needs.