How Much is Too Much
Sometimes it may seem as if a dog could eat endlessly. This is not true of course; a dog needs a certain amount of food each day. Just like humans, too little food will not offer the dog enough nutrients and vitamins and a Shih Tzu will not be able to properly grow. Health issues will eventually appear is a dog is underfed for an extended time.
Determining Proper Weight
Too much food and just like a person, your Shih Tzu will gain weight. When a dog is overweight this will first show in the rib area. A Shih Tzu has long fur so one can determine a general idea of proper weight by touching the rib cage.
If you can immediately feel ribs that are seem to be almost poking through the skin, your Shih Tzu is extremely underweight. If you can feel the ribs but also feel a thin layer of fat and muscle, your dog is most likely an appropriate weight. If you cannot feel the ribs at all because so much fat and tissue is covering them, your dog may be carrying too much weight.