Experienced and professional animal trainer provide their insights in answering this question :
A. These are very non specific symptoms. The weight loss could be due to not eating much. Othet symptoms would need to be checked by vet. Could be anything from worms to tumors.

How to Identify Common Pet Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced pet care professionals :

Increased water intake and weight loss are definitely cause for concern, and should prompt a visit to your veterinarian for an exam and blood tests. The two leading causes of these signs together would be kidney failure and diabetes mellitus.
Surgery, drug reactions, stress, heart disease, and other issues may also cause weight loss in canines. If your dog is refusing to eat, losing weight, or has any other digestive or feeding issues, play it safe and let the veterinarian take a look at your pet.
If your dog will drink water but won`t eat, it may be due to nausea, stress, or mouth pain. If they are able to keep the water down, that is a good sign.
Changes in diet (not including restricted-calorie foods), environment, or stress levels, including the addition of new pets, may lead to weight loss that is rarely permanent or significant. The more rapid the weight loss, the more potentially concerning it is.
Some common causes of a dog suddenly drinking a lot more water include kidney failure, diabetes mellitus, Cushing`s disease, or simply dehydration, all of which need to be addressed. If you notice your senior dog is drinking more water than usual, plan a visit to the vet.
Dogs can drink water excessively when they`re bored, hot, after eating salty foods or just because they`re simply dehydrated. However, there other causes that might explain why your dog is drinking so much water such as medication side-effects or possible illnesses.
In extreme cases of tapeworm infection, your dog may lose weight despite eating normally. This is due to the tapeworm feeding on the nutrients in your dog`s intestines. Like vomiting, weight loss can have a variety of causes.
A general rule of thumb for determining the amount of water a dog should drink daily is 1 ounce (1/8 of a cup) of fluids per pound of body weight. For example, a 10-pound dog should drink approximately 10 fluid ounces per day, while a 100-pound dog should drink roughly 100 fluid ounces in a day.
Add something yummy to the food.

Some kinds of baby food can also tempt a dog to eat. However, be sure to avoid any baby foods with onion or garlic as those ingredients are toxic to dogs. Adding some water to your dog`s dry food and allowing it to sit for a few minutes is another option.

While it is true that a large number of dogs tend to get chunkier as they age, some senior dogs start to lose weight.
When weight loss occurs in older dogs there is a good chance that it is caused by an underlying health condition. These issues include liver/gallbladder disease, dehydration, dental, kidney disease, heart disease, diabetes, cancer, and arthritis. Each one of these issues needs to be diagnosed and addressed by your vet.
As important as it is to avoid dehydration, there can be too much of a good thing. Many owners — and even some veterinarians — are unaware that an overabundance of water in a dog`s system can lead to frightening symptoms and even death.
Your veterinarian will first test your dog for the presence of glucose and ketones in the urine. If indicated, the next step is to measure your dog`s blood glucose concentration. The diagnosis only becomes definite when glucose is found both in the urine and at a high level in the blood.
Why Is My Dog Drinking Lots of Water and Licking Their Paws? These signs together can be caused by dehydration, allergies, pain, or even behavioral issues, including anxiety, stress, or cognitive dysfunction (the dog version of dementia).
Dogs need roughage in their diets and grass is a good source of fiber. A lack of roughage affects the dog`s ability to digest food and pass stool, so grass may actually help their bodily functions run more smoothly.
Depressed dogs may show symptoms such as a lack of interest in activities, loss of appetite, increased irritability, and unusually clingy or needy behavior. You can help improve your dog`s mood by giving them plenty of exercise, playtime, and mental stimulation.
Depression makes a dog extremely lethargic and tired, it`s normal for dogs to sleep for around 12 hours a day and spend the rest of their time playing, walking, eating and relaxing. When they`re depressed, you`ll notice them sleeping a lot more and they`ll lose interest in the things they usually enjoy.
‍Stage I: Usually, there`ll be no signs of kidney disease, and dogs will continue to act normal. If you bring them to the vet`s office, their blood work can appear regular, too. Ask your veterinarian about testing your pup`s symmetric dimethylarginine (SDMA) levels, which can indicate kidney disease.
Whether it`s due to parasites, or just getting into the garbage, dogs with vomiting and diarrhea will lose a lot of excess water. It is normal, therefore, for them to try to drink more to make up for these losses.
Worms that infect pets…

They live and grow inside the intestine of your pet. Roundworms* and hookworms develop from eggs into larvae (immature worms). The larvae later grow into adult worms. Most pets show no signs of infection with these worms, but some may vomit, stop eating their food, or lose weight.

How much water should my dog or cat drink? Textbooks define normal water intake as 1-2ml per kilogram of bodyweight per hour (equivalent to approximately 25-50ml/kg/24hrs).
In the end, it is largely up to you whether or not you give your dog water at night. For adults that are potty-trained, we absolutely recommend giving them water at night. There should be no reason that they can`t hold their bladder overnight.
Lethargy or Fatigue

A diabetic animal will often be more tired than usual and show an unwillingness to participate in some of its regular activities. Diabetes can cause weakness in certain muscles in an animal, and since they may suffer from malnutrition, they will spend more time sleeping and less time being active.

Symptoms of high blood sugar in dogs include:

Increased thirst. Increased urination. Depression, expressed in loss of appetite, changes in sleeping habits, loss of interest in activity, and/or seclusion. Severe depression, as seen in dogs with very high blood sugar levels.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. How do I determine how much my overweight pet should weigh?
ANSWER : A. There are many tools to determine overweight and obesity levels in pets. A new tool, morphometric measurements and body fat index, are available to accurately determine a pet’s ideal weight; this will allow an accurate determination of the amount of food a pet should receive to achieve weight loss. Feeding the correct amount will lead to greater weight loss success.

There are many weight loss food options to help pets reach their ideal weight. Your veterinarian can help make a ideal weight recommendation. Here are some tips to help your dog lose weight in a healthy and safe way:

1. Diet: Providing a healthy and well balanced diet is essential to your pet’s overall health. Finding the right food for your dog can be a challenging process. For those overweight animals many commercial dog companies offer weight loss diets, but it is important to evaluate food labels for adequate nutritional content.

You want to ensure you are not missing other essential vitamin or mineral content. Volume of food is also important and the amount of food that works for one breed of dog may not be the same for another breed of dog. Portion control as opposed to free-choice feeding can help your dog to drop a few unnecessary pounds.

There are also prescription weight loss foods designed by veterinary nutritionists, such as Hill’s r/d (http://bit.ly/1AoENSd). Some pet owners find that home cooking is the best option for helping to provide a well-balanced and realistic diet plan. There are websites such as balanceit.com that offers recipes to fit your dog’s specific needs. Consulting with your veterinarian or a veterinary nutritionist to find the appropriate diet is a great way to help your dog be as healthy as possible.

2. Exercise: Another great tactic for weight loss for your dog is exercise. Whether this is through running, walking or playing with a favorite toy all of these are wonderful types of exercise to help keep your dog at a lean and healthy weight.

For those pet owners with busy schedules utilizing professional dog walking services or playtime through dog daycare services is another option. It has been shown that those pet owners that exercise regularly with their pets generally live a healthier lifestyle.

3. Physical therapy: As animals age pet owners offer encounter their favorite canine having more difficulty walking and have a dwindling desire to play with toys. Physical therapy, specifically hydrotherapy is a wonderful way to help older and arthritic animals gain more mobility and lose weight. Hydrotherapy has been proven to have several therapeutic effects on the body including, muscle strengthening, relief of swelling, decreased joint pain, less stiffness in limbs, improved circulation, weight loss, and increased tissue healing to name a few. For more information on the benefits of hydrotherapy:
http://bit.ly/1w1qqoy

4. Veterinary visit and blood work: Weight gain can also be related to underlying health concerns such as hypothyroidism or other endocrine disorders. Scheduling a veterinary evaluation and routine blood work can be another important component in increasing the longevity of your dog’s life. Conditions such as hypothyroidism that predispose dogs to gain weight can be treated with a daily medication to improve hormonal balance. If feel that your dog is unnecessarily overweight there can be an underlying health condition that needs to be addressed.

5. Healthy treats: Pet owners love the chance to reward their favorite canine companion with treats and most dogs jump at the chance to consume these delicious products. The problem is many treats, which can include commercial dog treats or table scrapes can add many unnecessary calories to your dog’s daily intake. Reading labels and making note of the calories in these treats is an important component of understanding your dog’s overall health. Treats should not exceed more than 10 percent of your pet’s daily calories. There are healthier treats that can be offered to your pet to keep calories lower yet provide a fuller sensation. A pet owner can add steamed or pureed vegetables, such as carrots, green beans or sweet potato to add more fiber and thus a fuller feeling for your dog.

Q. My Cocker has recently started to lose a weight with a loss of appetite or eats very little. Has energy, drinks normal H20
ANSWER : A. These are very non specific symptoms. The weight loss could be due to not eating much. Othet symptoms would need to be checked by vet. Could be anything from worms to tumors.

Q. My pet shows weight loss and has a hard time walking, like he has lost strength in his legs and has no control to maintain balance. What’s wrong?
ANSWER : A. Loss of balance or inability to control the limbs can be caused by a wide range of problems and is usually cause for concern. Damage to the nerves or muscles can cause loss of balance, as well as neurological disease or some illnesses. Having your vet perform a complete examination is needed to determine the exact cause.

Weight loss can refer to the actual loss of fat and weight on your dog, or may also be due to the loss of muscle tone in the body. If there is a problem with one of the limbs, it may be that the weight loss you are seeing is actually loss of muscle in that area. Weight loss can again be caused by a wide range of problems from neurologic disease, illness, parasites or disease. Making an appointment with your vet is best.

Q. We have two female cats who are sisters. One was just diagnosed with generalized lymphoma. Is there risk of being contageous? What kind of food
ANSWER : A. Lymphoma is a cancer and not a bacteria or virus, so it cannot be spread from cat to cat via contact. However, if your cats are related, they may both be genetically predisposed to getting the same type of cancer. Feline lymphoma can also sometimes be caused by the Feline Leukemia Virus (FeLV) or Feline Immunodeficiency Virus (FIV) which CAN be spread from cat to cat. The spread of these viruses is usually through bite wounds, saliva or fecal and urine matter, and the chances of spread among two amicable cats is lower, however testing both cats is always good.

As lymphoma can cause a decrease in appetite, sometimes the best food is one that will keep your cat on her normal eating routine so that she keeps her weight and energy up. Enticing her to eat by warming up wet foods, or even moistening and warming dry foods may encourage continued normal eating and may prevent weight loss from loss of appetite. A high-fat, high protein and low carbohydrate diet (such as a grain-free diet) may also help by providing a more calorie and nutrient dense meal so that every bite is beneficial.

Q. My pet is overweight, what should I look for in a food?
ANSWER : A. There are many therapeutic food options available. These foods have been formulated to provide the proper nutrients with controlled calories or formulated to alter metabolism, so the pet will lose weight. Using over-the-counter wellness foods is not advised for weight loss. They have not been formulated for weight loss, so while calories can be restricted; nutrients will also be restricted, which could result in deficiencies in important nutrients, such as protein, minerals or vitamins.

There are many options for weight loss foods. There are restricted calories and fat foods; typically calories are replaced with fiber, water or air to give a feeling of fullness. The pet can eat the same amount, but receive fewer calories. There are weight loss foods that alter metabolism. High protein foods have been used successfully to alter metabolism to burn fat. Research has been completed using neutrogenomic technology to alter metabolism in dogs and cats.

Q. Why does my dog eat grass?
ANSWER : A. As another user mentioned, dogs can eat grass when they want to vomit. Sometimes, when a dog has an upset tummy, they will eat grass. If you notice your dog eating grass frantically, you can assume vomiting will shortly follow. Grass does not digest and pass normally. If your dog eats too much grass, it can cause serious issues with pooping. Your dogs poop can end up all tangled inside of her, and it can need veterinary assistance to remove it. The same goes for celery, so avoid feeding celery to your dog.

The other day my boyfriend accidentally left the laundry room door open where we were keeping the trash that was filled with cooked chicken bones. She ate one of the chicken bones lightning fast. We had to induce vomiting by feeding her some hydrogen peroxide. After we had fed her the peroxide, she immediately began frantically eating grass because her tummy was upset.

If there is something lacking in your dogs diet, it could be that your dog is eating grass to make up for it. I am sure that my dogs diet is extremely well balanced (I do not only feed her an air-dried raw food-type diet (Ziwipeak), but a wide variety of safe, healthy foods), so when she eats grass, I know that it is because she has an upset tummy.

That is why I think it is important making sure your dog has a very well balanced diet. If your dog is on a low quality kibble, your dog may be trying to let you know by eating grass (or eating poop).

Q. My dog hasnt eaten snce I left 4 days ago. I won’t be home for 6 more days. How can the caretaker get her to eat?
ANSWER : A. If your dog is feeling a bit sad while you are away and is refusing to eat, your pet sitter may try some things such as adding in boiled chicken or turkey to meals to encourage eating. A pet-safe gravy may also entice your dog to eat as well while you are gone. Your pet sitter may also want to offer smaller meals more often throughout the day to give your dog more chances to try and eat when she is feeling more comfortable and a little less sad. A game of fetch or playing together may also get your dog’s appetite going and help her to feel more comfortable eating around your pet sitter.

If your dog is showing any other signs of illness in addition to the refusal to eat (beyond normal missing an owner), then it is always a good idea to keep an eye out and contact a veterinarian as needed.

Read Full Q/A … : ufdc.ufl.edu

Q. My 16 year old indoor cat has lost most of her body weight in the last couple of weeks. I think she may have worms. What do I do?
ANSWER : A. Weight loss can be a serious sign of many underlying conditions in older cats, most notably metabolic issues such as thyroid disease or organ dysfunction. If no worms are visible in her stool, bringing in a stool sample to check for them, or making a wellness exam to check for any other causes of the weight loss are best to help find why your cat is losing weight prior to just treating for worms.

If worms are present, then determining the type of worms they are is the next step. Worms generally cause digestive upset in cats such as vomiting or loose stools in addition to weight loss in large infections. The two most common types include roundworms (long spaghetti-like strands) and tapeworms (small rice grain segments). Roundworms can generally be cured with any over the counter wormer, however tapeworms need a wormer specific to them to be given. Tapeworms are also spread via contact with fleas, so starting a flea prevention treatment can help prevent further infections. Cleaning all bedding and the environment your cat is in will also help for any type of internal parasite infection.