The Forever Dog Book Review – Nutrition for Longevity

This book and it’s authors probably do not need an introduction – almost everyone in the dog realm has heard of The Forever Dog book, and it’s co-authors Dr. Karen Becker and Rodney Habib. The book has sold out on multiple occasions, is a New York Times Best Seller, is published in multiple different languages, and is widely accessible (at a low price point of just $28.99 USD – it’s much more affordable than other programs such as the Cancer Series $197 USD).

I’ve been a fan of both of these authors for years – before I even had my own dogs I was watching and reading their online content about nutrition. I’ve always looked up to them and their ability to condense information into easy-to-learn formats. When I used to work with wildlife and started to transition into small animal practice (aka dogs and cats) – I have to admit – their “Biologically Appropriate” verbiage spoke to me. And when my pup Ash had gastrointestinal issues on traditional kibbled products, I started to reach for lower carbohydrate kibbles like Orijen, and raw diets like Primal to solve his problems.

But you know what? It didn’t work – he was worse.

After a presentation at a veterinary conference by board-certified veterinary nutritionist Dr. Sean Delaney, and some quick learning on how to use BalanceIT – we ended up on a low-fat cooked diet – you can see the recipe here. And guess what – he improved. Since then he has been on several more moderate protein and carbohydrate recipes – including the Just Food For Dogs Chicken and Rice and is thriving.

So though I highly respect these two individuals, and I understand their lived experiences have driven them towards their recommendations. We may agree on some things, but our opinions do differ on others. And these opinions differ because either research is conflicting, our experiences are different, and/or data is limited. The truth is – we don’t have much long-term nutrition research in dogs, so there is a lot of opinion & speculation in this space as far as “ideal” nutrition for longevity.

The Perspective of The Forever Dog

I think it’s important to understand the perspective of the authors who are writing this book. Both have seen the benefits of a raw, low carbohydrate diet for their dogs, and both have had experiences that were tragic with kibbled products.

Rodney’s first dog was almost killed during the 2007 melamine pet food recall by eating a kibbled product contaminated with a toxic substance. And Dr. Becker’s first dog was negatively affected by prescription dry dog food (I don’t honestly know this full story, only what I’ve read briefly in various blog posts). Both dogs were described as their “heart dogs”, and the kibble in question was Purina and Hill’s brands.

I can be sympathetic to anyone who has had negative experiences such as these, and understand why this perspective may drive them to pursue change in an industry. My own experiences drove me into fresh food as well.

Dog Food Recommendations in the Forever Dog

I picked up this book for similar reasons that most pet parents did – to see if I was missing something and if there was a place I could do more. However, I approached the reading of this book a bit differently – highlighting and then cross-referencing recommendations to research studies. Because if I was going to change my perspective and recommendations towards pet parents based on this book, I wanted to be able to cite research papers as to WHY I changed my opinion.

Obviously, there is no way to cover everything in one blog post – so I will highlight some key areas in regards to nutrition, and “the best diet” for dogs. And though I definitely do agree with some of these recommendations, there are others I think we may need more research on before making recommendations just due to the lack or limits of our current research

The very general nutritional recommendations of the Forever Dog book:

1. 10% of the diet should be “Core Longevity Toppers”
2. Time-Restricted Feeding to 8 hrs per day
3. Keep Your Dog at a Healthy Weight
4. Feed a “Biologically Appropriate Diet”
5. Feed a Less Processed Diet

A note here: I attempted to cross-reference based on textual context, names of researchers, and resources given on the website. There were no citations given in the text, thus it was at times extremely difficult (sometimes impossible) to find the primary source or research behind the recommendation.

Feed 10% of your dog’s daily calories as Fresh Food

Regardless of what type of food you feed your dog, instead of feeding 10% of their daily calories as biscuit treats – use those calories to “boost” the nutritional, and antioxidant properties of your dog’s food. They coined these as: “Core Longevity Toppers” or CLTs. Basically these foods are a variety of fruits and vegetables that are dense in antioxidants and phytonutrients.

Research:

A retrospective study from 2005 that looked at the rate of bladder cancer in Scottish Terriers found that feeding a small amount of either leafy green vegetables or orange/yellow vegetables three times per week decreased bladder cancer rates by 50%.

As a retrospective study was done on just one breed for one type of cancer it is hard to make over-arching claims when it comes to fruit/vegetable consumption and cancer rates. However, there is probably no harm to feeding dog-safe fruits/vegetables to our dogs, and this research suggests a large up-side of their inclusion into the diet.

Personally, I think adding a variety of fresh fruits/vegetables to the bowl is a great idea. And though we don’t have research to support it at this time - it’s possible that dogs can receive similar benefits from the antioxidants and phytonutrients as we do as humans.

Feed in an eight-hour window, Encourage Fasting

Time-restricted Feeding to an 8 hours window to allow for autophagy to occur.  The ideal recommendation from the Forever Dog Book was two feedings per day, with only healthy low calorie treats in-between for training purposes.

“Dr. Mattson has conducted studies in which he subjected animals to alternative-day fasting, with a 10-25% calorie-restricted diet on the in-between days. According to him if you repeat that when animals are young, they live 30% longer.

The Forever Dog, pg 144

“A growing number of experts recommend fasting healthy dogs (that weigh more than ten pounds) one day a week.”

The Forever Dog, pg 145

Research Dr. Mattson:

The above quote was referencing a body of research performed between 2014 and 2016 on mice. These mice were fed a very specific diet called the “Fasting Mimicking Diet”. True fasting was unable to be done in mice due to rapid weight loss, thus an alternative called FMD was created.

The “Fasting Mimicking Diet” was low protein, low sugar, and high fat. Twice per month mice we placed on this diet for 4 days between the age of 16 months to 24 months – and positive results were seen.

Mice had weight loss despite consuming the same amount of calories per day. Overall lifespan was 11% longer in mice who were fed the FMD diet twice per month. Researchers did note however that fasting in the same manner after 24 months of age showed negative results, and instead lowered the fasting window to 3 days, twice per month.

“the FMD cycles started at 16 month of age caused an 18% increase in the 75% survival point, and an 11% increase in the mean lifespan. Notably, after 24 months of age mice appeared to be negatively affected by the 4 day FMD, but not by an identical FMD reduced to 3 days”

This research shows us that mice fed a certain dietary composition, rotated in a certain increment has positive results for lifespan and weight loss. However also mentioned that fasting must be modified later in life, and does not speak to early-life (before 16 months). This research did not look at true “fasting”.

Research Dr. Panda:

A research study done in 2014 by Dr. Panda where they looked at mice fed several different types of diets in a restricted window while keeping amount fed (calories) equal.

These results were very interesting because depending on diet type – results varied! In the first test group mice were fed a high fat plus sucrose diet – one group was allowed to eat 24/7, the other group was only allowed to eat during a 9 hr window of the day. Mice consumed the same amount of calories. After this period of time the mice who were allowed to eat “whenever” gained 42% body weight, and the mice on a restricted eating window gained 21% body weight.

Now for the interesting part – the second group of mice was fed a high fructose, low-fat diet. Then broken into two groups – one allowed to eat whenever the other only allowed to eat during a 9 hr window. Mice consumed the same amount of calories. After this period of time BOTH groups of mice gained 6% body weight.

Meaning time-restricted feeding alone does not result in weight loss, it only happens with certain dietary compositions.

Personally, I’m still on the fence about fasting - though studies in mice have been promising. The overall thoughts in the human dietetics community are that “the benefits of intermittent fasting aren’t unique to not eating for a long period of time, but simply due to caloric restriction.” Dr Adrian Chavez, phD Nutrition. Further studies in humans where they reported improvements to blood pressure, blood glucose, asthma, and other metabolic functions with longer periods of fasting (greater than 24 hours) - but all these effects were lost with re-feeding.

Basically my take-away is this - if your dog doesn’t want to eat a meal or for a 24 hour period and they are otherwise healthy, and drinking enough water - it’s probably okay. I won’t try to force them to eat. But if your dog does best on eating several times per day, do not force them to eat in a certain manner. We don’t have the research to support any particular time frame for fasting or times per week/month that would be ideal for dogs to fast.

Instead I believe picking a meal schedule that works for you and your dog, feeding to ideal body condition.

Keep your Dog at A Healthy Weight

This is actually mentioned very briefly within the book but it’s very important, as we do have two different research studies that offer supportive data, including one lifetime study on dogs.

“Living an extra year or two because you’re a dog of normal weight may not seem like much, but in dog years that’s huge.”

The Forever Dog, page 18

Research:

A 14 year lifetime study done in 2002 by Purina found that by simply keeping your dog at a healthy weight you can extend their lives by 15% (about 1-2 years), and delay the onset of disease by that same time period.

“Compared with control dogs, food-restricted dogs weighed less and had lower body fat content and lower serum triglycerides, triodothyronine, insulin, and glucose concentrations. The median life span was significantly longer for dogs in which food was restricted. The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs.”

Further research submitted by Banfield Animal Hospital in 2018 saw that depending on breed dogs who were at a healthy weight for their lifetime lived significantly longer. With the Yorkishire Terrier gaining almost three years, and other breeds like German Shepherds only gaining 6 months.

The overall takeaway here is - keep your pup at a healthy weight. I am saddened that more focus wasn’t given to this aspect within the book as research supports that it causes such a significant difference to lifespan.

Feed a “Biologically Appropriate” Food:

A general recommendation of a diet that is composed of less than 20% Carbohydrates on a Dry Matter Basis was given within the book for several key reasons explained in this quote:

“Consuming 30-60 percent starch for energy delivers results similar to what we see in our kids in the fast-food world. That much starch creates lots of energy (and those calories can lead to obesity) and poor brain chemistry, inflammation, and nutrient deficiencies (overfed and undernourished) because the carb calories displace the much-needed calories from nutrient-dense meat.”

The Forever Dog page 290
Let’s break down the main claims behind the recommendation of a low carbohydrate diet for dogs, as I think these claims are stretching a bit from the research we currently have available.

Carbohydrates are metabolically stressful because they cause spikes in blood sugar.

First – just like with different cuts of meats or types of oils – all carbohydrates are not metabolized in the same way. Carbohydrates can be simple or complex (just like oils can be saturated or unsaturated), and fiber within carbohydrates can be soluble or insoluble.

Depending on the composition and the combination of carbohydrates, proteins, and fats within a meal blood glucose will respond differently. It is very rare that a carbohydrate is given in a vacuum without other dietary components. Even if a dog food contains a simple carbohydrate source, they usually also contain vegetables, protein, fat, and purified fiber (such as inulin or beet pulp) to slow sugar spikes.

It is also important to note that all the research on the negative effects of sugar consumption in humans focuses on “simple refined carbohydrates” or “simple sugars” in items like soda – not complex carbohydrates eaten in a meal. Human dietitians do not recommend to avoid carbohydrates – and we don’t have research in dogs that suggests avoidance either.

Carbohydrates are inflammatory to dogs.

Next let’s talk about carbohydrates being pro-inflammatory. We actually have research that says a combination of complex carbohydrates (containing soluble fiber – like in oats and wheat), along with omega 3 fatty acids reduces inflammatory markers (AGEs), and positively affect the microbiome.

Meaning carbohydrates can be anti-inflammatory – but this largely depends on overall dietary composition. Just like a diet composed heavily of poultry (high in omega 6 fatty acids) that does not contain adequate omega 3 fatty acids to balance would stimulate a more “pro-inflammatory” pathway. We don’t avoid poultry just because of this – we instead – balance our fats.

Carbohydrates are not nutrient-dense, and are not necessary.

I think there is a misunderstanding about the purpose carbohydrates may be used for? Carbohydrates can be utilized as a source of calories, a source of fiber, or a way to offset lowering protein or fat (for example for dogs with pancreatitis, kidney disease, liver disease, certain urinary conditions, IBD, weight loss, etc).

It’s also important to point out here that fruits and vegetables are not strictly necessary either. But they are beneficial (as they have described in detail within the forever dog book).

The digestibility of plant-based proteins (such as legumes) is not as good as animal-based proteins, however just because a food uses a plant-based protein doesn’t mean it cannot be utilized, you would just need to adjust for digestibility differences.

Plant proteins may also be paired with animal proteins in order to keep costs down and fill in essential amino acids while keeping ash content low. The classic example of this is research we have looking at the combination of combining corn gluten meal with a poultry meal (which is high in Ash/Minerals), this actually improves overall diet digestibility, while providing essential amino acids, and fats (at 91% protein digestibility).

Can fresh poultry meat be used as the protein source and maybe get a higher overall protein digestibility ? – Yes. My point here is to say that they don’t contain no nutrients, and no benefits.

They are calorically dense – leading to pets being overweight.

Protein and carbohydrates both have the same atwater factors (4 kcal per gram), if we were looking to make a food less caloricaly dense we would probably want to focus on fat content (9 kcal per gram). Research we have looking at weight loss in dogs promotes a high protein, high fiber, low-fat diet – which I talk about in detail on my blog post about weight loss for dogs.

Carbohydrates can definitely be included in a weight loss and weight maintenance diet successfully. Their inclusion within a diet does not cause weight gain – we don’t have research to support this.

They are not the diet dogs “choose” given the choice to do so.

The research behind this is fascinating: basically studies offering dogs meals that allowed them to self-select found that dogs preferred a diet that was high moisture, high protein and high fat – at first. After a period of time dogs started to reduce the amount of fat within their diet, and increase the carbohydrate content.

“He [Dr. Roberts] is most famous for his studies on how dogs would instinctually decide which foods to eat if given the choice. They don’t opt for the carbohydrates. Much to the contrary, they – live wolves – select calories coming from fat and protein first, and the carbs a distant lst.”

The Forever Dog Book, page 117

At the beginning of the 10 day feeding trial dogs ate a diet composed of 30% protein, 68% fat, and less than 2% carbohydrates. By the end of the diet trial period dogs preferences started to change – protein content raised to 44% , fat content lowered to 52%, and carbohydrates stayed relatively similar at 4%. All diets were offered “ad lib” meaning dogs could eat as much as they wanted, and all dogs gained significant weight by the end of the trial period.

A couple of limitations of this study – first it was only 10 days long, this is hardly looking at longevity – animals (including humans) will binge eat foods that they desire in short amounts of time leading to weight gain. And obviously weight gain is what we want to avoid when we consider a diet optimized for longevity. Personally, I’d love to see a longer study to see if dogs can normalize their caloric intake to maintain a healthy weight, and what that diet looks like. Because that might give us more clues as to “optimum” composition for longevity. Also tracking activity level and seeing if dogs could naturally adjust for metabolic needs.

My overall feelings on this recommendation are that we don’t have research to suggest which dietary composition is ideal for dogs (there have been no long-term studies), thus no research to support feeding a certain diet would make a dog live longer.

Also - every dog is an individual, and some dogs may not do well with this composition, it seems odd to not consider other factors like weight loss goals, concurrent conditions, and individual activity level in these recommendations.

Basically, if your pup does well on a low-carbohydrate diet - awesome. But saying it’s the best for everyone and causes harm seems a bit of a stretch?

Feed a less processed diet:

The Forever Dog Book recommends feeding a diet that is less processed, mostly to avoid/minimize exposure to Advanced Glycation End Products (AGEs) and Advanced Lipoxidation End Products. They also mention a list of other issues with “ultra-processed” foods.

“Fresh pet food advocates have a myriad of other issues with ultra-processed, all-in-one diets made by the pet food industry, including the following:

1. Pet food packaging doesn’t include all the information a human food label does, including sugar or carbohydrate content of food.
2. AAFCO owns the pet food ingredient definitions and you have to pay to know the official definition.
3. Digestibility studies are optional
4. No batch testing requirements for nutritional adequacy, contaminants or toxins
5. AAFCO allows for excessive amounts of other nutrients that could cause organ damage because of the lack of maximum values on certain nutrients.
6. Multiple studies have found that pet food products are not accurately labeled on their ingredients lists.”

The Forever Dog Book, page 74

Based on those two factors The Forever Dog Book makes the followering recommendations: Homemade (best), Gently Cooked or Raw (pathogen controlled), Freeze Dried, Dehydrated, Canned, Air-Dried, Baked, Dry (extruded), Semi-Moist (worst).

Personally, I would argue this list (quoted above) is a pet food industry problem - not a fresh vs. processed food problem. We don’t see fresh food companies jumping to do any more research or quality control than their kibbled counterparts. But I do agree that these are problems within the pet food industry that need to be addressed.

I’ve long advocated for batch testing for nutritional adequacy, pathogens, and toxins using a “test and hold” procedure. I think random testing for nutritional and ingredient purity should be performed - with enforcement! And I believe regular digestibility studies should be done on all pet foods. You should always speak to your pet food company and ask them questions about their product prior to feeding it.

AGEs & ALEs and Pet Food Research

That aside – let’s talk about AGEs and ALEs for a minute – because this area of research is extremely interesting (and NEW!).

“A 2018 study out of the Netherlands found dogs consume up to 122 times the AGEs in their diets than humans… when the levels of AGEs in different dog food categories were compared, AGEs were highest in canned food, followed by dry food. Not surprising, the lower amount of AGEs were fond in minimally processed raw foods.”

The Forever Dog Book, page 67/68

The study mentioned in this quote was part of a review paper published in 2018, however the original research was actually published in 2014. Further research on AGEs has been published in 2020 looking at raw and kibbled products. 

According to this research, twice as much AGEs were found in the urine of dogs on kibbled products to those on raw diets (0.28 vs 0.57 CLM). At this time we don’t really have an established “acceptable range” for AGEs in dogs, however, it has been noted that dogs fed extruded diets have similar expression of AGEs as humans eating ultra-processed foods (such as fast food).

AGEs (in particular Maillard Reactions) occur when a protein and carbohydrate (glucose ), where they form a bond that makes the protein indigestible. The processing method of combining proteins with carbohydrates while cooking at high temperatures may lead to more AGE formation – which seems to occur more with kibbled and canned products.

But it is important to note that research on individual human foods, cooking method and AGE production is highly variable. Even some raw foods naturally have higher levels of AGEs. Overall recommendations in the human food sector to reduce AGEs are:

“Animal-derived foods that are high in fat and protein are generally AGE-rich and prone to new AGE formation during cooking. In contrast, carbohydrate-rich foods such as vegetables, fruits, whole grains, and milk contain relatively few AGEs, even after cooking.”

This research suggests the inclusion of carbohydrates (which is contradictory to previous recommendations within the Forever Dog Book), and lean cuts of meat rather than high-fat grinds. It also advocates gentle cooking methods to help limit AGEs formation in food items.

But overall research in this area is still in it's infancy - and maybe with more research, the pet food industry as a whole can make adjustments to processing methods to account for AGEs formation? But current research does point out that currently there are more AGEs in kibbled and canned products - suggest a fresher, less processed diet might avoid this. But we don't have established "recommended safe" amounts for dogs at this time. I'm looking forward to following research in this area in the future to see what more we can learn.

Final thoughts:

There are many other recommendations in this book, including ingredients to avoid, and a discussion on synthetic supplements, along with discussions on the microbiome – which I may cover in a future blog post (as this one is already VERY long).

There are also recommendations on exercise, stress management, cleaning products, lawn products air fresheners. As I’m not an expert in behavior, chemical compounds or canine rehabilitation I don’t really think I can comment on this sections other than to say – I’ve realized my dogs DO get less exercise than before I had kids (I have too!). Thus I’m pretty sure my goal going forward will be for all of us to get outside on walks more often – even if I have to enlist help from family/friends so I can keep track of everyone (walking two dogs with two toddlers is no joke!).

I also really appreciate the statement made in this book about it not being “all or nothing”, it can be just a little bit of a change. And I think that goes with all our goals for life – small changes over time can make a huge difference for our health. And though I may have seemed critical in this review – I do still think the book is worth a read, and I do believe fresh food provide benefits for dogs (exactly how much – I’m not sure yet – it might depend on multiple concurrent factors that have yet to be evaluated). I just ask that you are skeptical of recommendations, and to seek the original research (and your veterinarians guidance) prior to perusing changes to make sure they are in the best interest of your dog.

So my general thoughts are: keep your dog at a healthy weight, add in some fresh food to the diet, feed a balanced diet optimized for your dog’s individual needs, go on adventures together, and enjoy life with your pup.

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