Introduction
It can be worrying if your older dog starts losing weight even if they’re still eating their food. While weight loss can sometimes indicate an underlying condition, it’s not always something to worry about. Subtle weight changes in a dog’s later years can be fairly common.
It can be a good thing if your senior dog is more slim than plump, as it can mean less pressure on their joints. However, if your dog becomes underweight, they’ll need more calories to get back to a healthy weight. So if your senior dog is looking slimmer than they used to, then it’s a good idea to keep an eye on them to make sure they’re not losing too much weight.
In this blog, I’ll be sharing my advice as a nutritionist on what to do if your senior dog is losing weight but is still eating. I’ll explain why this happens, when this may be a cause for concern and how you can help your dog maintain a healthy weight in their golden years.
Key takeaways
- Age-related conditions like sarcopenia can cause a senior dog to lose weight, as well as changes in metabolism or how they absorb nutrients.
- An increased metabolism caused by conditions like hyperthyroidism and Cushing’s disease can mean a dog loses weight despite eating a lot of food.
- Monitoring your dog’s weight loss by noting down physical changes, checking their BCS score and regularly weighing them can help you keep track of their weight changes.
- Symptoms like vomiting, diarrhoea, weakness, lethargy and increased thirst are signs that your dog should get checked out by your vet.
- Senior dogs can benefit from calorie and nutrient dense diets to help them regain weight and stay healthy and comfortable in their later years.
Table of contents
Is it normal for senior dogs to lose weight?
Why is my senior dog losing weight but still eating?
Common causes of weight loss in senior dogs
Other signs that may appear alongside weight loss
What to feed a senior dog losing weight
Monitoring weight changes in older dogs
When to speak to your vet
Is it normal for senior dogs to lose weight?
It’s normal for a dog’s body to change as they get older. While some dogs put on a little weight,
others lose some. This can be due to several reasons, including sarcopenia, an age-related condition that causes a loss of muscle mass in older dogs. This can make a dog look thinner, particularly in their hind legs. [1] As dogs age, it becomes harder for them to absorb all their nutrients, and they may also have a slower metabolism.
While age-related changes are normal, if you’ve noticed sudden and significant weight loss then it’s something to keep an eye on.
Do senior dogs lose weight as they age?
When your dog gets older, you may notice subtle changes in their weight, which is normal for seniors. However, sudden weight loss should be monitored, as it may be a sign of an underlying health condition.
Why is my senior dog losing weight but still eating?
It can be confusing when you notice your dog losing weight, but they’re happily licking their bowl clean. If you’ve noticed weight loss on your otherwise healthy dog, it could be because of a number of reasons. Your older dog may not be absorbing nutrients properly, which can lead to weight loss even if they’re eating their usual amount. Dogs can also burn energy differently as they age, which can cause some notable weight changes. Dental problems, digestive troubles, and medical conditions can all be reasons behind weight loss.
Common causes of weight loss in senior dogs
There are a few common reasons why a dog may be losing weight despite eating. These include:
- Digestive problems
- Metabolic conditions
- A loss in muscle mass
- Parasites
Digestive problems and poor nutrient absorption
One reason why a dog may lose weight without losing their appetite is because they may not be absorbing all their calories. There are some conditions that can cause this, like inflammatory bowel disease (IBD), which is a syndrome caused by the irritation of the intestinal tract. Over time, this syndrome can disrupt the absorption of nutrients. [2] The common symptoms of this include: vomiting, diarrheoa, and reduced appetite. Other gastrointestinal troubles like chronic diarrheoa and stomach ulcers can affect a dog’s weight.
Metabolic conditions
Metabolic conditions like diabetes and hyperthyroidism can result in a dog burning calories much quicker than normal. This can explain why they are still losing weight despite eating just as much food as they normally do.
- Diabetes is a common disorder that happens when a dog’s body cannot regulate blood sugar normally. The symptoms include weight loss, increased thirst, and lethargy. [3]
- Hyperthyroidism is a rare condition that happens when there is an overproduction in hormones in a dog’s thyroid gland. This can increase metabolism, resulting in weight loss. [4]
- Cushing’s disease is an endocrine disorder that affects middle-aged and senior dogs. This disease happens when a dog produces too much cortisol. The symptoms of Cushing’s disease include increased thirst, hair loss, panting and weight loss. [5]
Dental problems
Another reason why your dog may be losing weight could be due to dental problems. This can cause pain and discomfort when eating, which is why your dog may not be eating enough resulting in weight loss. Also, senior dogs may struggle to chew properly if they have dental problems, even if they appear to be eating.
Parasites
Intestinal parasites like roundworm, hookworm, tapeworm and whipworm can cause weight loss in dogs, even if they have a normal appetite. Dogs can become infected with worms if they eat contaminated soil. They can also be infected with worms before they’re born if their mother has them. However, tapeworms can only be passed on through fleas. [6] Common symptoms include:
- Diarrhoea
- Vomiting
- Nutritional deficiencies
- Swollen abdomen
- lethargy
If your dog has worms, they’ll need a trip to the vet to be treated.
Cancer or chronic illness
One possibility behind sudden weight loss in dogs is cancer, which affects around 1 in 4 senior dogs. While some cancers aren’t curable, there are treatments available like chemotherapy and radiation that can extend your dog’s life. Symptoms can include: unexplainable weight loss, behavioural changes, lethargy, masses and lumps. Many people find that grooming or brushing their dog is an ideal time to check for any lumps and bumps, as well as checking their body condition by feeling their ribs – they should be easy to feel, but not too prominent.
Other signs that may appear alongside weight loss
If you’ve noticed your dog has lost weight, it’s good to keep an eye out for other symptoms that could indicate that they need to be seen by a vet. For example, if your dog is suddenly very thirsty and is urinating much more frequently, this could be a sign of dehydration, Cushing’s disease, diabetes or kidney failure.
Losing weight but acting normal
When a dog suddenly loses weight but appears to otherwise be healthy, it could indicate the early stages of a health problem. This is why a trip to the vets to get your senior dog the care they may need is important.
Increased appetite
Sometimes a dog can lose weight but still have a ravenous appetite. Some parasites can cause this behaviour, or metabolic conditions like diabetes. An increase in a dog’s metabolism can make them super hungry, but also means they burn through calories a lot quicker, which explains why they lose weight but keep eating.
Weak back legs
If your dog seems to have weaker back legs, it may be due to muscle loss or an underlying health condition. This could be from sarcopenia, which involves muscle loss which is especially prominent in the hind legs.
Hair loss
Some hormonal disorders could cause a dog’s fur to thin alongside weight loss. Hair loss can be due to fleas, ticks, hyperthyroidism and Cushing’s disease. [7]
What to feed a senior dog losing weight
Older dogs can struggle to absorb all the nutrients they need, which means their diet may need to be adjusted as they get older so they can get the calories and nutrients their body needs to maintain a healthy weight. To help support your dog as they age, they can benefit from highly digestible protein sources like chicken and turkey. Your dog could also benefit from calorie-dense foods to help them gain weight. There are foods made specifically for senior dogs’ needs, although every dog is different so it’s best to chat to your vet on what may be best for your dog if you’re considering altering their diet.
How to help your senior dog gain weight safely
To help your older dog reach a healthy weight, you could try feeding them smaller, more frequent meals which gives them more opportunities to eat, and will be less likely to overwhelm them. If their appetite is low, you could try warming their food up with bone broth or switching to wet food to help encourage them to eat more. You may also want to try switching to nutrient and calorie-dense food – although with Tails.com, our clever Adaptive Nutrition system will automatically begin to switch your adult dog onto senior food based on data including their age, breed and size.
If you think your senior dog might be underweight, you can carry out a simple Body Condition Score (BCS) test at home, looking closely at their body shape and feeling their ribs through their fur to check how much fat and muscle they’re covered by. Then, if it turns out your dog is underweight based on this and their measurement on the scales, all you need to do is update your dog’s BCS and weight on your Tails.com profile, and our team will send out higher calorie food to help them get to a healthy weight. While some senior dogs require fewer calories, dogs that are losing too much weight should have more. It’s important to remember that weight gain takes some time; slow and steady is the right approach.
Before changing your dog’s diet, a trip to the vets can rule out any underlying health conditions that may be causing weight changes. Your vet can also advise you on how you can help your dog get back to a healthy weight.
Monitoring weight changes in older dogs
If you’ve noticed a weight change in your older dog, you may want to keep an eye on it to make sure they stay a healthy weight. Regular weighing and keeping track of their appetite, behaviour, and any physical changes are effective ways to do this. You can also use the BCS chart to examine their weight, as well as weighing your dog on the scales at home or taking them to the vets where there will usually be a set of scales you can use.
When to speak to your vet
While weight changes in senior dogs can sometimes be a normal result of ageing, unexplained weight loss should be checked out by a professional. Your dog may have a medical problem that they would need treatment for so they can return to their happy and healthy selves.
Call your vet if your dog’s weight loss persists or any of the following symptoms appear:
- rapid weight loss
- weakness or lethargy
- vomiting or diarrhoea
- changes in appetite or thirst
Conclusion: Supporting your senior dog’s health as they age
Changes in weight in older dogs is relatively common, but it shouldn’t be ignored. If you’ve noticed your senior dog has lost a bit of weight, then it could be down to a medical reason which you may not be aware of. It’s best to get them checked out by a vet to rule out any underlying conditions and get advice on how you can help your dog get the nutrients and calories they need to be happy and comfortable in their later years.
FAQs
Is weight loss normal in older dogs?
Subtle weight changes are common in older dogs, but sudden weight loss can indicate a health problem, which would need to be checked out by a vet.
What food helps senior dogs gain weight?
Foods that are calorie-dense and nutrient-dense can help a senior dog put on some weight. Before changing their diet, it’s important to rule out any underlying conditions that could be behind the weight loss.
When should I worry about weight loss in my dog?
We understand that weight loss in dogs can be very worrying. If your dog has unexplainably lost weight and is experiencing symptoms like vomiting, diarrheoa, weakness and lethargy, it’s best to take a trip to the vets to get them examined.
Sources
[1] Sarcopenia in Dogs: Understanding Muscle Mass Loss in Senior Dogs, PetMD, August 20, 2025.
[2] IBD in Dogs, PetMD, October 7th 2022.
[3] Diabetes in Dogs: Causes, Signs, and Treatment, PetMD, updated November 14th 2025.
[4] Hyperthyroidism in Dogs, PetMD, November 10th 2022.
[5] Cushing’s Disease in Dogs: Symptoms, Diagnosis, and Treatment, PetMD, updated July 9th 2025.
[6] Intestinal worms in dogs, BlueCross, page last updated on 09/03/2026.
[7] Hair Loss in Dogs: Causes, Symptoms, and Treatment, PetMD, April 23rd 2025.