Joint and muscular problems can be complicated by obesity. Liver and skin problems occur more often. Diabetes is an added risk. Obese dogs also are more susceptible to to pancreatitis. These health problems are no doubt expensive to treat, but they also can shorten the dog's life and threaten his quality of life.
Some beagles are tall and slender, others shorter and quite muscular.
Rather than relying solely on weight, a good test for obesity is to physically palpate your dog, checking for the rib cage. If you can easily feel your dogs ribs and spot a waistline when viewing your beagle from above, then it probably isn't overweight. Dogs that appear to be overweight may have hidden medical conditions, so please consult with your vet before beginning any weight-loss program. This is something you need to discuss with your veterinarian. Your vet may suggest additional exercise, changes in feeding habits and reduced-calorie dog food to help slim down your dog.