Nutrient numbers in dog food labels can't always be treated as high = good and low = bad. A few general guidelines for thinking about the role of key nutrients in maintaining the health of your pet:

Protein

The building blocks of muscles and other body tissue. High amounts may be good for working or sporting dogs, or older dogs at risk of losing muscle mass. Overweight dogs often do better on a higher protein diet during weight loss. Excess protein is converted to blood sugar (carbohydrate), so more isn't always better for your average pet. Some dogs with special conditions, like liver failure, may do better on a lower protein diet.

Fat

Fat is an energy-rich source of calories and is used in large amounts at rest by most dogs. Essential fatty acids, present in diets, are critical to skin and coat health as well as regulating inflammation. Some dogs have sensitivities to higher fat diets, like those with pancreatitis.

Carbohydrates

Carbohydrates in complex form, like those found in whole foods, are a source of calories which provide blood sugar. Many carbohydrate sources also bring with them phytonutrients and other beneficial compounds. High carbohydrate diets are often needed when dogs have to avoid protein and fat due to medical conditions. Low carbohydrate diets may be helpful for weight loss.