Always consider what you are rewarding. Associate the command with the action with the reward. The more dramatic you make your signals and body language, the better response you'll get from the dog. Now is not the time to be self-conscious. A serious look at canine diet and nutrition.
Good nutrition is key to maintaining health and a long and happy life.
Unfortunately, Pudgy Pooch, Picky Pooch has been taken out of print by the publisher. The comparison of Shetland pony to Clydesdale or Chihuahua to Irish Wolfhound is certainly striking. Better to be safe and stick with what you know. This has actually been demonstrated in wolf relocation programs. Canadian wolves moved to parks in the United States continued to feed on their customary prey where possible even though new prey species were now available to them.