How to Evaluate How Much to Feed Your Dog

sk an animal nutritionist what is the most frequent question asked by dog owners about pet food and you'll be surprised to know that it's not "what should I feed my dog", but "how much should I feed".

This guide explains the simple math you can do to calculate how much you should be feeding your dog on a daily basis, based on his metabolic needs.

It’s currently estimated that over 50% of dogs in North America are overweight or obese. Carrying extra weight isn’t cute or cuddly—it will shorten your pet’s life, create unnecessary discomfort, and can lead to serious chronic diseases. To prevent obesity, the primary concern, should be how many calories to feed daily.

With commercial pet food, you can easily be fooled to think that measuring food is simple—you just read the feeding instructions on the label and you’re done. Nothing could be further from the truth, and following blindly these instructions can lead to overfeeding.

“Let your food be your medicine, and your medicine be your food.” Hippocrates

How do I know if my dog is overweight?

Unfortunately, most owners of overweight dogs seem to have no awareness of the problem. In the 2018 clinical survey run by the Association of Pet Obesity Prevention, less than 22% of owners of overweight dogs were aware of their dog's weight problem.

Evaluating your dog only involves monitoring his weight regularly to check if it's stable. 

One method is simply to look at your dog's body shape from above (take a photo once a month to see is there are notable changes). You can also feel the rib cage. With an overweight dog you won’t be able to feel the ribs with a flat palm. If you can see the ribs, then your dog is underweight.

The other method is simply to use a weighing scale once per week and to chart the results to check for abnormal weight changes. Both methods are commonly used by veterinarians during check-ups.

Start by checking the normal range of weight by dog breed on the AKC website, and ask your vet to tell you the optimum weight for your dog based on his breed, health and age.

What to feed vs how much to feed

Dogs are omnivorous—just like us—which means they can eat almost any food and get the necessary nutrients from it. Essential nutrients are fats, proteins, and carbohydrates. 

The staple diet of dogs living in a natural setting includes other animals, carrion, and occasionally fruits and grasses. Half of the calories in the ancestral diet were from protein —primarily from fresh animal sources—providing half of the calories in a dog’s natural diet. Today, typical commercial dry food has on average half as much protein (26% of the calories) and 7 times more carbohydrate (40% of calories) as a dog's ancestral diet.

We could easily assume that a dog instinctively eats what he needs until he feels fulls, but it's a wrong assumption, for 2 reasons:

1. Some dogs are greedy eaters (anyone with a Labrador?). Because they are by nature opportunistic scavengers, dogs instinctively gobble all they find in the dish (you never know when the next meal will come and who will compete with you for it). That's the result of 10,000 years of evolution.
2. Dry food like kibble is high in starches (glucose). It doesn't give a feeling of satiety and raises insulin levels so that blood sugar spikes more frequently and dogs gets hungry more often. Dogs fed on kibble eat more of the wrong nutrients (carbs and fats), and not enough of others (proteins).

The amount of food matters less than the proportion of nutrients — fats, proteins, and carbohydrates— that are fed, and how many calories it translates into.

The problem with commercial dog foods 

Commercial dog foods consist of protein, fat, carbohydrate, fiber, water, fiber and ash. The total of these components equals 100%. Ash is the leftover from extruded kibble food cooked at very high temperatures, and fiber is the non-digestible carbohydrate of a plant.

All dog food and treat packagings are required to include a guaranteed analysis, listing protein and fat as minimums, and fiber and moisture as maximums.

The first issue is that the guaranteed analysis does not tell us the most important information, the percentage of calories from protein.

The second issue is that the guaranteed analysis does not list the carbohydrate content of the food. We need to calculate it ourselves (fortunately, it’s easy).

The third issue is that to evaluate and compare the true nutrient content of dry foods, we must first deduct the moisture (water) content from the product evaluated, and calculate nutrients on what is called the dry-matter basis (DM).

How to calculate carbohydrate content

The following table gives you a comparison of typical adult pet foods, comparing dry and canned food, and calculating the carbohydrate content and true protein on dry-matter.

The things to note are that dry food has a high carbohydrate percentage, and that canned foods have a much higher true protein content.

To calculate carbohydrate content, subtract the protein, fat, moisture, ash and fiber from the total weight of the food. In the example above, the digestible carb contents (without fiber) of the dry food is equal to (26% — 15% — 6% — 4% —10%) / 100 = 39%.

Differences between dry and canned foods

Canned food has a high water content of approximately 75% (comparing to 10% for kibble). Once you remove water, you can compare the protein content of both types of food by dividing the protein percentage by the dry matter percentage. 

• Canned: 10% protein divided by 25% (100-75%) = 40% protein 
• Kibble: 26% protein divided by 90% (100-10%) = 29% protein

In the example above, canned food has more protein content than dry food, even though the listed protein of dry food on the label is much higher.

Calories vs food servings

Pet foods vary greatly in calorie content, even among foods of the same type and formulated for the same life stage. Feeding directions also vary among manufacturers, so the number of calories delivered in a daily meal may be quite different between products.

Food provides energy in the form of calories. In pet food, calorie content is labeled in a thousand units and in relation to food weight (kcal/kg) and servings (kcal/cup). 

Food calories come from fat, carbohydrates, and protein, but not in the same proportions. Fats provides 9 kcal/gram of caloric energy (the amount of usable energy obtained from the food), more than twice as much as carbohydrates and proteins which provide only 4 kcal/gram, depending on the quality of the food.

In the example table below, fats provide 34% of the calories for energy, but the minimum fat amount is labeled at 15%. This matters because the type of fats used in the diet (omega-3 vs saturated fats) has a important impact on your dog's health. With a homemade diet, you can feed your dog fresh quality protein for optimized calorie intake (instead of less digestible carbs), and choose unsaturated fats from fish oils that are healthier.

How to calculate your dog's calorie requirements

The number of calories (kcals) that your dog needs for his metabolism each day depends essentially on 2 things:

• Your dog's weight
• Your dog's activity or energy level (nutritionists use a scale from 90 to 130; at the lower end, 90 is equivalent to a senior dog who might go for a short walk once a day, 110 is your average adult dog, and on the high end of the scale 130 is a highly active working dog).

Dogs can vary in size from 4 to 200 pounds. With such wide ranges, how do you figure out how much food your dog needs? A 4 lbs Chihuahua does not necessarily use 50 times less energy than a 200 lbs English Mastiff.

To solve this weight/energy problem we can adjust a dog's weight using the Metabolic Weight (MW) calculation based on the energy a dog needs to perform essential body functions (called Resting Energy Requirements ). Small dogs have a proportionally higher metabolic weight than large dogs.

Finally, to determine how many calories to feed, a further adjustment of the Metabolic Weight (by factors between 1.2 and 3) can take into account factors such as life stage (puppy, adult or senior), whether neutered or intact, and the dog's health condition.  

A formula for calculating calories

A useful food calories calculator is available online if you're not good at maths.

If you want to calculate your dog metabolic needs yourself, you just need to follow these 3 simple steps (you'll need to use a scientific calculator):

1. Convert your dog’s weight in pounds to kilograms by multiplying by 0.45.
2. Multiply the weight (kg) raised to the power 0.75 to get the MW (x^y on a calculator).
3. Multiply the MW by your dog's estimated activity level (by a factor between 90 and 130, the average being 110) to get the calorie amount in kcals/day.

If you think 1.500 kcals is high for a 65 lbs dog, consider that a racing sled dog competing in a 100-mile race can consume 8,000 kcals/day and still lose weight! On the opposite end, a couch potato of the same breed and size needs less than 1,000 daily kcals.

Home prepared food

Home prepared food, whether raw or cooked, would logically seem more difficult to measure—you cannot easily figure out calorie content per food weight, and each meal is likely to include slightly different foods. In fact, it's almost impossible to calculate precisely the nutritional content of a home-prepared diet. The best strategy is to feed a variety of fresh ingredients each day, rotate the ingredients, and balance the diet over time.

To figure out how much to feed an adult dog, the simple rule of thumb is to calculate 2 to 3% of the dog's optimal body weight. Ask your vet for your dog's optimal weight in pounds, and multiply the weight by 16 to convert to ounces. Then multiply his weight in ounces by 0.02 (32%) or 0.03 (3%) to get the daily amount to feed.

For example, my active 65 lbs Golden Retriever should be fed 3% of his optimal body weight, which works out to be 30 ounces (850 g) of fresh food daily (65 x 16 x 0.03).

Conclusion

Dry foods typically have high levels of digestible carbohydrates (starches). Carbs are metabolized in glucose and stored as body fat when unused, therefore these foods are more likely to produce overweight dogs due to overfeeding. Think about what would happen if your daily diet consisted exclusively of sandwiches made with white bread.

The best strategy to keep your dog healthy is to figure out his metabolic weight (MW), estimate the number of calories you need to feed each day, and choose foods containing unsaturated fat sources. You should also monitor your dog's weight on a regular basis to ensure there are no significant changes.