Hill's nutritionists & veterinarians developed Prescription Diet r/d clinical nutrition specially formulated to support dogs' weight loss. It helps metabolize fat and maintain lean muscle, helps your dog feel full & satisfied and supports a healthy immune system. Hill's Prescription Diet r/d Dry Dog Food is intended for intermittent feeding only and is not recommended for long-term feeding (over 6 months). Please consult your veterinarian for further information on how our Prescription Diet foods can help your dog to continue to enjoy a happy and active life.