Weight Loss Diets for Dogs Fact or Fiction?

Posted in: Articles

Posted on: 24 January 2012

Weight loss diet for the dog? What kind of new craziness is this! I can just hear my elderly neighbour’s words echoing in my ears as I start to write this blog, but he’s not alone.  Sadly, overweight dogs are still considered something to laugh about with competitions being run to find the country’s fattest pooch and photos being the focus of much hilarity on the nation’s TV breakfast sofas. 

The current estimated figures for overweight and obese dogs in the UK is anywhere from 1/3 to ½ of the entire dog population.  This is not a fluffy and humorous subject made for joking, it is a serious and often fatal issue for our canine companions.  Keeping a dog consistently above a lean or ideal body condition has been proven to result in reduced lifespan of almost 2 years[1], as well as increasing the risk of multiple associated health conditions.

What is Fat?

Contrary to what we’ve believed for years, the last decade has revealed that fat is actually an active tissue and does more than simply provide insulation against the cold and store energy for us.  Research has demonstrated that fat actually produces a group of proteins that are now being linked to some of the ailments often present in obese animals.

Obesity - The Disease

Obesity is officially classed as a disease and sadly it is the most common nutritional problem seen in the nation’s dogs today.  There are numerous risk factors that can contribute to the development of obesity in our pets, but fundamentally it results when energy intake exceeds energy expenditure i.e. fuel in is greater than that being burnt off and used.  This means that it is a disease that is both preventable and treatable.   

Risk Factors for Obesity

In order to tackle the issue, we need to understand what the risk factors are.  By identifying the ones that are pertinent to your dog and minimising them (where possible), this gives you the power to prevent weight gain in the first place. 

1. Genetics

There are specific dog breeds that are predisposed to weight gain. In the UK these include (but are not limited to) Labrador Retrievers, Golden Retrievers, Collies, Cocker Spaniels, Dalmations, Rottweilers, Dachshunds and Beagles.

2. Gender & Neuter Status

Female dogs have been shown to be more likely to gain weight than male dogs.  Additionally, any dog that has been neutered is more prone to gaining weight due to the hormonal changes that take place

3.    Lifestage/Age

Older dogs are more at risk of increased weight gain and this is partly linked to a slowing down of metabolism, as well as an association between increasing age of dog and increasing age of owner

4.    Activity Level

Decreased physical activity increases the risk of weight gain

5.    Diet & Feeding

Feeding a high fat diet, excessive treating, providing human food and allowing free-choice/ad-lib feeding is also associated with obesity

6.    Social Aspects

The relationship between food and emotion can also contribute to weight gain, as food derives emotional rewards for both owner and dog

7.    Secondary to other disease

Obesity can be associated with endocrine conditions such as Diabetes Mellitus, Hypothyroidism (an underactive thyroid) and Hyperadrenocorticism (overactive adrenal/pituitary glands)

8.    Secondary to medication

Obesity can also develop with long-term use of certain medications that increase appetite e.g. steroids

If your dog is already overweight and has been identified as having a Body Condition Score above ‘ideal’ by your vet, then you will need to start a veterinary monitored weight loss plan that addresses all elements of both you and your dog’s lifestyle.

So, why and how are veterinary specific weight management diets different to ‘light’ or ‘low fat’ dog foods? 

Different Definitions

Trying to navigate the pet food aisle of the supermarket or pet store reflects the current shift and literally the growing trend in our canine population.  We are surrounded by pet foods emblazoned with the words ‘Light’, ‘Low Calorie’, ‘Reduced Fat’ and many more – but what does any of it actually mean?

Any product with the words ‘Light’, ‘Low Calorie’, ‘Calorie Control’, ‘Reduced Fat’ or ‘Low Fat’ on the labelling should mean that the pet food has an overall lower fat and calorie content, when compared to standard pet foods of the same category and lifestage.   Although they may support small quantities of fat loss in overweight dogs, they are preferable for aiming to prevent weight gain in susceptible dogs.   Overall these foods generally help to maintain your pet at ideal weight and body condition, rather than inducing specific weight loss. 

Believe it or not, overweight and obese dogs actually have more or less the same energy requirements as their leaner and slimmer selves. This is because unhealthy weight gain is predominantly comprised of fat.  However the underlying muscle layers remains more or less unchanged.  Fat tissue, unlike muscle, requires very little energy to maintain it and generally speaking overweight/obese dogs are less active.   So, although you may already have cut his food intake back to what he should be having were he at his ideal body condition or have switched him to a ‘light’ version of his normal pet food, his weight has probably stabilised.  He may no longer be gaining weight, but he’s also unlikely to be losing any.

Specific Weight Loss Diets

Specialised weight management diets that are recommended by your vet help to support safe and healthy weight loss in your dog.  The current advice is to aim for 1-3% reduction in body weight per week.  Any more than this is considered akin to crash dieting and can be dangerous. 

Different dogs also tend to adapt and lose weight differently on individual weight management diets and sometimes this is due to palatability or ingredients or it may simply be due to their own unique response.  Happily, there is a range of weight management diets available in the UK and all of them are specifically formulated to have reduced calorie quantities, whilst also maintaining complete and balanced nutrient levels.  Whichever diet your vet recommends however, it will most likely have been created with some or all of the following specialised features and ingredients.

Low Fat Content

All commercially produced weight management dog foods contain less fat than comparable diets for maintenance (i.e. food for dogs already at their ideal weight and body condition).  This is because fat contains over twice as many calories per gram than either protein or carbohydrate.  In other words, it is hugely energy dense.  By restricting the level of fat in the overall food product, this results in less energy/calories being available per portion.


One of the challenges that pet owners struggle with when putting their dog on a weight loss plan is the concept that their dog will be hungry.  In fact, if they elect simply to reduce the volume of their normal dog food then, aside from the risk of nutrient imbalance, this will be the case!  Pet food manufacturers have overcome the issue by addressing satiety i.e. feeling full.   Subsequently many weight management diets will have increased levels of protein and fibre, which in addition to their other benefits also provide a filling effect for your dog. This then helps to reduce hunger and begging between meals. 

High Protein Content

Aside from its effect on satiety, a higher protein content also results in fewer leftover calories.  The body has to work harder to release energy from protein, than it does to release it from carbohydrate.  This is because glucose is the primary source of fuel for the body and is itself a carbohydrate in its simplest form.  So, by working harder to obtain energy from protein, there is less overall energy for the body to store as fat. 

Furthermore, as muscle is made up of protein a high protein diet ensures that muscle tissue is maintained during weight loss, whilst fat is preferentially lost.  Protein also has an impact on palatability and just like us humans, dogs generally find fat-restricted diets a little less tasty.  So, although protein won’t be quite as palatable as fat, by increasing the level of high quality protein in the food from sources such as chicken or beef, your dog is likely to find it more appealing and be more willing to eat it.


The type and quantity of fibre used in the diet is also important.  Soluble fibres such as psyllium or inulin, have a beneficial effect on the bacteria in the gut and also slow down the time it takes for food to pass through the system, which allows more time for nutrient absorption including glucose.  Insoluble fibres on the other hand such as cellulose, produce a bulking effect on the faeces, which stretches the gut wall and helps to regulate bowel movement.  However, fibre can also have some less desirable effects as it attracts water in the gut, which makes for a softer and sometimes more voluminous stool.  It can also contribute to flatulence! So the blend of fibres in the food is a very important factor for consideration.

Additional Ingredients and Neutraceuticals

1.    L-Carnitine

This is a specific amino acid that supports the preferential use of fat as a fuel source for the body.  As it is one of the building blocks of protein, it is generally present in and used by muscle tissue.   By adding it specifically to weight management diets, it can help to maintain muscle mass whilst stimulating the burning of fat for energy requirements.

2.    Glucosamine & Chondroitin

Overweight and obese animals often suffer from osteoarthritis and other painful, degenerative joint conditions, which are worsened by added pressure on the joint due to the excess weight being carried.  Glucosamine and chondroitin are referred to as chondroprotective agents as they help to protect and support joints by building up the cartilage and joint fluid itself. 

3.    Omega Fatty Acids

Whilst it might seem counter-intuitive to supplement a weight loss diet with additional fats, the benefits of omega 3 fatty acids far outweigh any potential adverse effects.  Obesity promotes inflammation and fish oil has an anti-inflammatory effect as well as enhancing the overall health of skin and coat.

4.    Antioxidants, CLA and FOS

Obesity enhances the oxidation process and this translates to damage of individual cells and larger tissue structures, as well as increased insulin resistance.  Antioxidants help to arrest this oxidation process and CLA (Conjugated Linoleic Acid) although still under much debate has been shown to have a beneficial effect on diabetic animals as well as increase lean muscle mass at the expense of fat.  FOS (Fructo-oligosaccharides) also known as prebiotics, have been shown to decrease faecal odours by promoting good gut bacteria over bad.


There is no doubt that the area of weight loss diets for our dogs will continue to be a focus of research in coming years.  With new science emerging all the time, this is an exciting field to watch, but realistically whichever diet works for you and your dog is the one that’s worth investing in.   Ultimately however, if you can extend your dog’s life by nearly 2 years or 15%, which is the equivalent of approximately 10 human years, isn’t prevention the best way forward?

[1] JAVMA, Vol. 220, No. 9, May1, 2002, pp.1315-1320


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