Over the years I have studied several subjects that sounded interesting at first but in fact turned out to be quite dull. My archaeology class in college was a stunning disappointment; the only things I really took away from that one were that Indiana Jones was not a true archaeologist, and that archaeology — as practiced by my college professor — is tedious and boring. My vet school reproduction class, as well, turned out to be nothing but a tedious study of hormone cycles, mostly in farm animals. Dogs and cats were covered only briefly, but at the time vet students were brainwashed with the “all dogs and cats must be spayed and neutered the instant a vet lays hands on them” philosophy, so their hormone cycles received short shrift.

And then there was nutrition. Nutrition, for small-animal (that means dogs and cats) vets, is an important subject. And indeed the portion of the class dedicated to dogs and cats was quite interesting. However, the months that were devoted to esoteric micronutrients in pigs, sheep, and cows were stultifyingly horrible.

Mammalian bodies are markedly complex things, and nutrition is by nature a complicated thing. But as most people who are living without nutritional deficiencies (which, I imagine, includes basically everyone reading this) can attest, if you exercise common sense, feeding yourself isn’t really that difficult. I’m happy to say that the same thing generally holds true for dogs.

In fact, in humans in the developed world the most serious nutritional problem that exists is overconsumption of calories. People simply eat too much, and they become obese as a result. It turns out that this is also the most common nutritional problem for dogs. Obesity is a serious health risk for our canine companions.

People are often concerned about the potential for their dog to become overweight. Less commonly, owners of dogs who are underweight (such as dogs who have recently been rescued from hoarders or other suboptimal situations) ask for guidance on helping their dogs increase their weight to healthy levels. This means that one of the most common questions I receive from pet owners boils down to, “How much should I feed my dog?”

It turns out that nutritionists, like economists, are very fond of mathematical formulas. I have always suspected that the formula obsession in both fields is an attempt to make the practitioners of the subjects feel more scientific — although frankly the mathematical formulas in both fields seem more pseudoscientific to me (although, to the credit of the economists, nobody acts like their subject is an inherently interesting one).

So, for those of you who want to know and like esoteric mathematical approaches to problems, your dog should be fed a multiple of his resting energy requirement. His resting energy requirement (RER) in calories is calculated as 70 times his body weight (in kilograms) to the 3/4 power. Or:

RER = 70(body weight)^3/4

Charts, such as this one, provide the various multiples necessary to complete the calculation. If you are looking for weight loss, your dog should be fed 1.0 X the RER for his ideal (desired) weight. If you are aiming for weight gain, then feed him 1.2 to 1.8 X RER for the desired weight. To maintain their weight active dogs and younger dogs need higher multiples of RER; older dogs and sedentary dogs need lower multiples. So all you need to do is guess your dog’s ideal weight, accurately guess the multiple he should receive, determine the caloric content of your dog’s food, grab a calculator, and voila, you know how much to feed him. Simple.

In fact, I think the above method is hogwash. Dogs have highly variable individual metabolisms. And what defines an active dog? One who goes on two leashed walks a day? An Iditarod sled dog? The formulas look so precise but are predicated on a massive amount of guesswork. That guesswork ruins the precision of the formulas and renders them totally pseudoscientific, in my opinion.

Fortunately, there is an easier way to feed your dog an appropriate amount of food. And I’m happy to say the way does not require a calculator and it works for all types of food.

First, choose a high quality, nutritionally complete and balanced diet. Such dog foods will generally be labeled as “complete and balanced.” Recipes for complete and balanced homemade diets are available through veterinary nutritionists and reputable online sources.

Next, know what ideal body weight looks like. Dogs at an ideal weight will have palpable but not overly prominent ribs and spines. They will have a noticeable waist behind their rib cage and in front of their hips. Your vet can help you determine whether your dog’s weight is ideal or needs adjustment.

Finally, feed your dog the amount of food that leads to an ideal weight. You can use the feeding chart on the back of the dog food bag as a rough guideline, but remember that it is a very rough guide indeed. In reality it offers nothing more than a starting point. In general the charts will lead to overfeeding (more food gets sold that way, after all), so I recommend starting with a little less food than the chart recommends.

Keep track of your dog’s body condition. If your dog is too heavy or is gaining undesired weight, then exercise him more and feed him slightly less. I usually recommend reducing food by about 10 percent and then reassessing a week or two later. Similarly, if your dog is too thin or is losing weight in an undesirable way, then feed him a little bit more (and keep on exercising him — exercise is fun and healthy for dogs) and reassess every week or two.

In theory, nutrition is more complicated than rocket science. Fortunately, in practice, feeding dogs appropriately is not hard at all.

Learn more about dogs with Dogster:

• The 10 Biggest Misconceptions About Guide Dogs for the Blind
• 6 Things to Remember When You Have a Fearful Dog
• Four Things You Should Know About Your Dog’s Growl

Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)