It easy to think that a pet is underweight, whereas the reality could be that he is just less heavy than an obese dog of the same breed that you happen to know. Maybe your dog is actually fine, but it's the other dog that is too fat! For dogs that are thin but full of energy and producing formed feces, the first step is to check they are getting enough calories per meal. A dog may lose weight because it uses up more calories than it is eating. This may be straightforward -- as when the dog isn't being fed enough food. If this is the case, then increasing his portion size should do the trick.  The simplest way to do this is compare your dog's ideal weight with the suggested feeding amount on the food packaging. If your dog is a specific breed, there is lots of information online about what is that breed's ideal weight. Go with the weight you want the dog to be, rather than the weight it is at the moment. For example, if you own a male Labrador then an average sized dog should weigh up to 40kg. Measure out a typical portion of your dog's daily food allowance by weight. Make a note of the weight of the food and compare it to the recommended amount from the food packaging.  It's interesting to note that some of these recommendations are actually 25% above what the dog needs (they tend to be on the generous side, rather than the skimpy side). If you are giving your Labrador 400g of kibble a day, and the packaging advises 500g a day, then your dog is being fed 20% less calories than the recommended and so it will lose weight. This is easily rectified by increasing the amount of his daily allowance. This can be a difficult decision because each food contains different amounts of calories and the size of dogs vary so much. As a rule of thumb, increase the food by no more than 10% of the original quantity.  So if you were feeding 400g a day, an extra 10% adds another 40g, which you would split into 2 meals of 20g each additional. Feed this for 2 -3 days and check the dog doesn't have diarrhea, at which point you can add another 10% and so on. Suddenly feeding way more food is a recipe for disturbing the balance of the bowel and causing diarrhea. Much safer is to gradually increase the portion size and monitor the dog's toilet to make sure it is coping.  If the difference in ration is not large, then divide the extra between two meals. If the difference is large, then adding in an extra meal (rather than making the existing ones larger) will be more gentle on the bowel.  If the dog gets diarrhea it is then losing precious nutrition and so your efforts are for nothing.
افحص الوزن الفعلي للكلب مقارنةً بالوزن المثالي للسلالة. تأكد من كمية الطعام المناسبة من أجل الوصول للوزن المثالي للكلب. قارِن بين ما تُطعمه لكلبك وكمية الطعام الموصى بها. قَرّر إلى أي مدى يمكنك زيادة الطعام اليومي للكلب. زِد كمية الطعام التي تقدمها لكلبك تدريجيًا.