Supports weight loss while maintaining muscle mass. Natural Prebiotic Fructooligosaccharides (FOS) in Eukanuba has been clinically proven to support strong defenses. Provides the appropriate levels of protein, carbohydrates and fat to maintain muscle mass while supporting weight loss or maintaining weight at an acceptable level. Recommended for medium breed dogs weighing 20-55 lbs. Natural Prebiotic Fructooligosaccharides (FOS) in Eukanuba has been clinically proven to support strong defenses.