Carb Metabolism

I've noticed lots of reports of cats getting fat off high-carb foods, especially prescription diets. One thing I don't understand, though, is that the carbs aren't supposed to be metabolized very well by cats. So then why does the cat get fat? Wouldn't they have to have a high insulin response AND metabolize the carbs?

Cats gain weight for the same reason humans do, by consuming more calories than they burn. If a cat is more likely to over eat (consume more calories than needed) a high carb food in my opinion it is because cats require a high level of protein and so may over eat a high carb, low protein food in trying to satisfy its protein needs. Also, dry foods tend to be high in carbs and are more likely to be fed in excess because they can be left out all day for the cat to munch on at will.

Here is an interesting article on obesity in dogs and cats by a well respected vet, Dr. Debra Zoran:

http://www.2ndchance.info/diabetescat-obesityZoran.pdf

Here's a study you might find interesting:

Gonadectomy and high dietary fat but not high dietary carbohydrate induce gains in body weight and fat of domestic cats

BTW, I'm sure sure what you mean by "[color= rgb(24, 24, 24)]carbs aren't supposed to be metabolized very well by cats.". Cats can metaboloize (derive energy from) carbohydrates.[/color]

mschauer said:

 
BTW, I'm sure sure what you mean by "carbs aren't supposed to be metabolized very well by cats.". Cats can metaboloize (derive energy from) carbohydrates.

Click to expand...

Yes, but it depends upon the form of carbohydrate. http://jn.nutrition.org/content/124/12_Suppl/2563S.full.pdf

And as Dr. Hodgkins, D.V. M., Esq. explains in her book, "Your Cat: simple new secrets to a longer, stronger life," (and one of the leading authorities on feline diabetes), on p. 6:

"In the liver, protein amino acids are processed into glucose (sugars) and sent into the bloodstream to supply the body's need for this energy nutrient. In a meat-eating species like the cat, accustomed to little dietary carbohydrate in its evolutionary environment, the liver will manufacture the great majority of the animal's needed glucose, which is the primary energy supply for the animal's brain. Because there is little glucose in a high-meat diet, this is an essential task for an obligatory carnivore. The liver of omnivores, including people and dogs, have multiple enzyme systems for handling dietary carbohydrate; the cat has only one such enzyme system, with limited capacity to deal with high carbohydrate consumption."

Basically...

The liver of most omnivorous animals has two enzymes, glucokinase and hexokinase, which catalyze the phophorylation of glucose to glucose-6-phosphate. Hexokinase has a low Km for glucose, whereas glucokinase has a high Km and operates mainly when the liver receives a high load of glucose from the portal vein. The activity of glucokinase in the liver of the cat is extremely low, whereas the activity of hexokinase is in the normal range (Ballard, 1965). Carnivores with omnivorous dietary habits, e.g. domestic dog, possess both enzymes."

Click to expand...

This is from the Nutrition Research Council, "Nutrient Requirements of Cats:" http://books.google.com/books?id=Jz...kinase in cat carbohydrate metabolism&f=false


Cats and dogs (well, carnivores) convert protein to glucose - the process is called gluconeogensis. Dogs are able to "downregulate" gluconeogensis based on the amount of carbohydrates in the diet - but cats cannot. So while they utilize carbs, they still need a certain amount of protein in order to prevent sabotaging their own lean muscle mass.

Dr. Lorie Huston (I think she works for Iams or something, but still..) has a discussion that helps make the carb thing easier to understand: http://suite101.com/article/the-role-of-carbohydrates-as-nutrients-in-the-diet-of-dogs--cats-a262422


As does Dr. Peterson, a small animal vet, specializing in endocrinology: http://endocrinevet.blogspot.no/sea...0-05:00&max-results=20&start=14&by-date=false

mschauer said:

BTW, I'm sure sure what you mean by "[color= rgb(24, 24, 24)]carbs aren't supposed to be metabolized very well by cats.". Cats can metaboloize (derive energy from) carbohydrates.[/color]

Click to expand...

I'm not a dietician or biologist, so I probably have some concepts wrong or am at least wording something wrong. Most of what I read is saying that cats should be fed a high protein diet and that they have a hard time deriving nutrients from plant-based foods. I've often heard that use of cranberries for urinary health would probably not do much as it is a plant. Made it seem like much of plant-based foods would simply pass through the cat much like fiber. But if cats are getting fat from carb rich foods, then something must be getting processed.

Really, I think it's that most cats that get fat are free fed, which means kibble, which is usually high carb. But when I switched to raw, and wasn't sure how much food they needed, by cats on a diet that was about 70% protein and 1% carb, gained weight, until I figured out how much food they need. So cats feed too many calories get fat, period.

Now - what role carbs (or certain carbs) play in inflammation-related diseases is a different subject - one yet to be explored in research, I believe. Cats can USE carbs, and some of them can be metabolized rather efficiently despite the low level or lack of glucokinase activity, especially if they're cooked (kibble/canned) or ground up - but their bodies, from an evolutionary standpoint, are not designed to derive their needed nutrition and energy from them.

LDG said:

Really, I think it's that most cats that get fat are free fed, which means kibble, which is usually high carb. But when I switched to raw, and wasn't sure how much food they needed, by cats on a diet that was about 70% protein and 1% carb, gained weight, until I figured out how much food they need. So cats feed too many calories get fat, period.
Now - what role carbs (or certain carbs) play in inflammation-related diseases is a different subject - one yet to be explored in research, I believe. Cats can USE carbs, and some of them can be metabolized rather efficiently despite the low level or lack of glucokinase activity, especially if they're cooked (kibble/canned) or ground up - but their bodies, from an evolutionary standpoint, are not designed to derive their needed nutrition and energy from them.

Click to expand...

I agree to that.... And if you have an obese cat on kibbles, wet, whatever, even when high carbs like I did and switch to raw feeding pretty much no carbs like I did... You will see that you feed too many calories, and no matter the theory, kitty will get fat.
Now.....
Where you can REALLY tell how much of the food the cat is digesting/metabolizing..... That answer is in the poop! :lol3: Kibble poops are huge, the more junk and the more problems the cat has to digest it, the bigger the poops, I have noticed.... Next is canned.... Raw poop is not only tiny, but they don't even poop everyday. To me, that clear difference in waste output means they are using/metabolizing raw much better than the other foods.... :nod:

The feline digestive system has a limited ability to metabolize carbs because it's designed (as Laurie mentioned) to process animal-based protein and fat. The amount of energy that can be obtained from carbs is further limited due to the cat's shorter digestive tract - only so much "energy" can be "freed" in the amount of time it takes to traverse the tract (even taking into consideration the fact that carbs move through more slowly than protein and fat). In addition, there is the (also previously-mentioned) upper limit to how many carbs can be processed at one sitting.

That said, some carb energy can be metabolized. And these carbs, even under such restrictive conditions, are closely linked to weight gain primarily because animal-based protein and fat are metabolized first - since cats are metabolically adapted for preferential use of animal protein and fat as energy sources (they're processed more easily and quickly because the feline body is built to metabolize and use exactly those sources) - and are immediately put to use fueling body functions, maintenance and repair. Furthermore, some of the cat's energy requirements MUST be met by animal-based protein, either from their food or, failing that, from their own bodies (thus we have older cats, with their increased need for protein, losing muscle mass).

If the cat obtains enough enough energy from protein and fat to meet all of their energy requirements, naturally, the energy from carbs, once it's freed, is stored as fat. However, because of their preferential bias towards protein and fat, even when only their most basic needs are met, the energy from carbs is still shunted into storage, resulting in cats that live but are, by-and-large, undernourished, lethargic, moody and overweight.

Free-feeding contributes to obesity because the food is available at all times, allowing a small but steady intake of carbs that never reaches the cat's upper limit of processing capability... meaning the max amount of carbs that can be metabolized are metabolized.

Lori Huston says that carbs, "play an important metabolic role in canine and feline nutrition" but she's only half-right. Without the protein and fat needed to meet their full energy requirements - basic functions as well as repair, growth and activity - cats fed standard commercial diets survive by utilizing what they can of their carb-heavy foods to meet the most basic needs, leaving the remaining requirements unmet. They live, but in addition to being obese and often apathetic, their immune systems are depressed and they get hurt and sick quicker and are slower to heal and recover.

This is why one of the most dramatic and consistent changes seen in cats transitioned to raw diets is a breath-taking leap in energy and vitality, including increased playfulness and affection.

Some of this is further explained here: Cats, Carbs and Calories: An Obligate Carnivore’s Perspective.

AC

Raintyger said:

mschauer said:

BTW, I'm sure sure what you mean by "[color= rgb(24, 24, 24)]carbs aren't supposed to be metabolized very well by cats.". Cats can metaboloize (derive energy from) carbohydrates.[/color]

Click to expand...

I'm not a dietician or biologist, so I probably have some concepts wrong or am at least wording something wrong. Most of what I read is saying that cats should be fed a high protein diet and that they have a hard time deriving nutrients from plant-based foods. I've often heard that use of cranberries for urinary health would probably not do much as it is a plant. Made it seem like much of plant-based foods would simply pass through the cat much like fiber. But if cats are getting fat from carb rich foods, then something must be getting processed.

Click to expand...

I thought your concern was strictly about weight gain. Like I said, weight gain is just about calories and cats certainly do derive calories from carbohydrates.  In fact, the Atwater factors used to estimate the mobilizable calories a cat derives from carbohydrates is the same as that for protein.

Now the bioavailability of nutrients is another a totally different story. 

mschauer said:

I thought your concern was strictly about weight gain. Like I said, weight gain is just about calories and cats certainly do derive calories from carbohydrates.  In fact, the Atwater factors used to estimate the mobilizable calories a cat derives from carbohydrates is the same as that for protein.

Now the bioavailability of nutrients is another a totally different story. 

Click to expand...

I mainly just wanted to understand the whole avoid high carb, feed protein advice better. It seemed contradictory -- cats can't utilize carbs very well, but cats get fat off of 'em.

Thanks everyone, for your replies! The amount of information needed to take care of kitty right seems endless...

I mainly just wanted to understand the whole avoid high carb, feed protein advice better. It seemed contradictory -- cats can't utilize carbs very well, but cats get fat off of 'em.

Thanks everyone, for your replies! The amount of information needed to take care of kitty right seems endless...

Click to expand...

I think part of the reason this all "seems endless" is due to the fact we're not just talking about what's right and healthy for cats, but every step of the way, we're actively fighting our way through a huge, nearly overwhelming program of misinformation. Walking 500 yards across a grassy meadow and thrashing through 500 yards of dense, thorny underbrush are very different endeavors! And unfortunately, we're stuck with the latter. *sigh*

AC

Raintyger said:

I mainly just wanted to understand the whole avoid high carb, feed protein advice better. It seemed contradictory -- cats can't utilize carbs very well, but cats get fat off of 'em.

Thanks everyone, for your replies! The amount of information needed to take care of kitty right seems endless...

Click to expand...

Well, when it comes to the protein vs. carb thing, it's really not complicated at all. :dk: From an evolutionary and metabolic standpoint, cats have a high requirement for protein, and no requirement for carbohydrates. Cats thrive on a diet high in protein and very low in carbs. Their natural diet (based on an analysis of feral cat diets from around the world), is, on a dry matter basis, 62.7% protein, 22.8% fat, 11.8% ash (minerals - e.g. from bone), and just 2.8% carbs (essentially none of which was found to be fiber).

The raw diet I currently feed my cats is 73% protein, 19% fat, and 1% carbs.

Raintyger said:

I've noticed lots of reports of cats getting fat off high-carb foods, especially prescription diets. One thing I don't understand, though, is that the carbs aren't supposed to be metabolized very well by cats. So then why does the cat get fat? Wouldn't they have to have a high insulin response AND metabolize the carbs?

Click to expand...

I think cats gain weight from carbs because they DON"T utilize carbs very well. They use protein and fat for energy first. The leftover un-used carbs are then stored as fat.