Eggs are rich in protein and are suitable for your dog if you don't overdo them. However, while egg whites can be given in higher quantities, high quantities of the egg yolk could increase the cholesterol level. Hence, feeding them moderate amounts of egg yolk and high amounts of egg whites is recommended. Red meat, which is more affordable, is considered healthy for your dog, mainly because it doesn't affect them the way red meat affects humans. In addition, beef is rich in protein and fats, and it could prove to be effective for your underweight dog.