The relationship between rider weight and horse welfare is a sensitive but important welfare topic, with evidence that excessive loading causes back pain and lameness.
Carrying excessive loads causes measurable musculoskeletal stress in horses, including elevated cortisol, altered gait, and back muscle damage. Horses cannot express this pain in human-legible ways until lameness or behaviour problems develop. The welfare issue is compounded by the emotional sensitivity of the topic - horse riders who are overweight for their horse may resist guidance. Welfare-centred conversations require sensitivity but cannot be avoided.