Instructions
Take your boxer to a veterinarian if it is underweight to determine the cause. If there is an underlying cause, treat it and ask the veterinarian what your dog's goal weight should be.
Feed your dog a wet food diet; wet food contains less carbohydrates than dry food and is more substantial. Increase the amount your dog eats daily by 25 percent of its current diet.
Supplement your dog's food with daily vitamins available through your veterinarian or from a holistic pet store.
Feed your dog treats between meals after good behavior. This will add calories to your dog's diet and reinforce its training. Satin balls are a good choice for dog snacks; they are balls of meat and grains that you can make at home.
Exercise your dog every day by taking walks, gradually adding more exercise to its daily activity. Boxers are muscular dogs and building muscle helps them gain body mass.
How to Fatten Up My Boxer Dog
Boxers are a stocky, medium-sized breed of dog weighing about 60 to 70 pounds at a healthy adult size. Boxers require daily exercise in the form of walks with their owner, as well as time to run and play outdoors. These dogs have a naturally large appetite so they usually gain weight easily. Their high level of energy helps keep boxers at a healthy weight. However, some boxers may require weight gain due to illness, pregnancy or other reasons. When this happens, fattening up your boxer is important to maintain its health.