Ettinger: Textbook of Veterinary Internal Medicine, 7th Edition

Weight Management

Sean J. Delaney

Andrea J. Fascetti

Why does obesity occur?

Overweight and obese pets appear to be an increasing problem. The abundant supply of highly nutritious and high calorie foods and treats, coupled with a less active lifestyle in many cases, inevitably results in the storage of the excess energy as fat. Over thousands of years, dogs and cats have survived, in part, for their ability to efficiently accumulate this body fat in times of plenty in preparation for times of famine. Wen food was scarce animals with the largest fat stores had the greatest likelihood of successfully surviving. Now that these animals are pets, they no longer undergo periods of famine.

Because our pets are not adapted to the concept of constant feast they readily gain more and more fat. In fact, the excess of fat has become so commonplace that abnormally large accumulations of fat have become the accepted norm. Accumulations of fat over the ribs that prevent them from easily being felt and indistinguishable waistlines are often not recognized as cues that a pet is overweight or potentially obese.

Why is obesity a concern?

Overweight pets are at increased risk for developing many diseases such as diabetes mellitus, arthritis, and breathing problems. In dogs it has been shown that they also have a shorter lifespan by up to 2 years. Thus keeping pets lean can greatly improve both quality and quantity of life. Few medical conditions with such severe adverse consequences can be so readily treated effectively. Veterinarians have become increasingly aware of the importance of weight management as a key component of preventative veterinary medicine.

How is obesity determined (Is my pet fat)?

Prevention of obesity starts with close monitoring of every pet’s amount of body fat through the use of a body condition score (BCS). A BCS is simply a number grade that describes the amount of fat that a pet has accumulated. Some systems use a 5-point scale and others use a 9-point scale.

A BCS scale is used in the following manner:

· A BCS of 1 indicates that a dog or cat is too thin
· A BCS of 5 (5-point systems) or 9 (9-point systems) suggests that a pet is obese
· A pet that is a “3” (5-point systems) or a “4” or “5” (9-point systems) has an ideal body weight
· Each point above or below 3 for the 5-point system is 20% to 30% over- or underweight, or 10% to 15% for each point above or below 5 on the 9-point system.
Determining a pet’s body condition score is much more useful than simply using their body weight as a guide to determine whether they are overweight since there can be a large variation in appropriate body weights for different sized pets. For example, it is difficult to know if a 65-pound Labrador retriever or a 1-pound Maine coon cat is overweight, but if they are judged to have a body condition score of 6 out of 9, we know that they are each approximately 10% to 15% overweight.

How is a weight loss plan developed?

Pets that are overweight and at risk of becoming obese or pets that are already obese can benefit from a weight loss plan. Weight loss plans are designed to achieve steady weight loss while keeping the pet as comfortable as possible. It is generally recommended that pets lose no more than 2% of their body weight per week. Rates greater than 2% are associated with feeling (and acting) hungrier, a slowing of the pet’s metabolism (making weight loss even more difficult), and preferential burning of muscle for energy rather than body fat.

Surprisingly, some pets only need 50% of the calories calculated using body weight alone to maintain their weight, whereas others need up to 50% more. Because of the large amount of variation from pet to pet, a veterinarian’s best clue to the amount of calories that a specific pet needs is determining from the owner the pet’s current caloric intake. Getting an accurate and complete list of all foods and treats (a diet history) that the pet is currently fed allows the veterinarian to calculate the amount of calories the pet is receiving and helps to ensure that the weight loss plan does not excessively restrict or provide too many calories. On some occasions a diet history cannot be completed. In those cases, the veterinarian uses the pet’s current weight to create an initial recommendation.

Whichever approach is utilized, the long-term success is completely dependent on following the pet’s response to the recommendation. Even with the most accurate and complete diet history and the best calculations, the initial weight loss plan may not result in weight loss of around 2% of body weight per week and can, at times, even result in weight gain. Therefore veterinarians use regular body weight checks during the weight loss period to adjust the amount of calories fed to maintain a consistent rate of weight loss. It is common for pets just starting a program to need multiple weight checks to achieve the desired rate of loss. This period of adjustment is more common when a pet’s diet history cannot be used for initial recommendations. This is why every attempt to determine a pet’s current caloric intake is made prior to initiating a weight loss plan.

Can the current food be used if attempting weight loss?

Since the amount of calories fed inherently must be reduced to result in weight loss, the volume of food will also need to be accordingly restricted if the pet’s regular diet is to be used. Veterinarians usually do not use a pet’s current food for weight loss, in part to avoid this reduction in volume. Smaller volumes do not distend the stomach as much and can lead to the feeling of hunger. Therefore most veterinarians initially choose to feed a special low-calorie diet designed for weight loss and not the pet’s regular diet. Most of these diets contain fewer calories per cup or can than atypical maintenance diet or even an over-the-counter “light” pet food. Switching the diet allows a similar volume of food to be fed while still reducing the amount of calories that the dog or cat is receiving.

These special weight loss diets have another advantage over a typical diet – almost all have increased amounts of essential amino acids, fatty acids, vitamins, and minerals. Pets undergoing weight loss only need fewer calories; they do not need less essential nutrients. Feeding a typical maintenance diet in an amount necessary to cause weight loss places the animal at risk of developing multiple nutrient deficiencies. Pet food manufacturers design their food to contain a specific amount of a nutrient per calorie. If the amount of calories were to be reduced by 30%, then all of the nutrients are reduced by 30% as well. Although a small excess of each nutrient is added for safety, the restriction in calories necessary for weight loss most often exceeds this safety margin, causing a standard diet to become deficient. Therefore diets designed for weight loss are often prescribed to ensure that the pets feel as full as possible, as well as to ensure their nutritional requirements are met.

A few diets designed for weight loss are not lower in calories but rather are lower in carbohydrates and higher in protein and fat to potentially change a pet’s metabolism to utilize more fat. This dietary strategy is untested for clinical efficacy and is usually used only when traditional, low-calorie weight loss diets have failed.

What about treats?

An equally important component of a pet’s diet is treats. Treats provide a pet with feedback that they are important members of the family. Accordingly, veterinarians will often strive to include some treats into a weight loss plan. Although any treat can generally be fed, treats should be limited to no more than 10% of a pet’s daily caloric intake. This decreases the potential of creating a nutrient deficiency since most treats are not complete and balanced foods.

It can be surprising how many calories some treats contain. For example, 1 tablespoon of peanut butter has the same number of calories as 3 cups of air-popped popcorn without butter. Many people with pets are equally surprised to find out that pets will often eat lower-calorie treats equally as well as those containing more calories.

Is exercise important?

An additional way to increase a pet’s sense of being appreciated is to play or walk with them. This also has the added benefit of providing the pet with much needed exercise during weight loss, which assists with the burning of fat and the increasing of muscle mass. The use of laser pointers and feather toys to encourage stalking and predatory behavior in cats can be very useful in increasing activity. For dogs, retrieving thrown objects or taking them on progressively longer walks can be an effective means of increasing their activity.
How will I know if the weight loss plan is successful?

Many people wish to know what their pet’s ultimate weight should be. Some veterinarians are reluctant to provide a weight because it focuses on a number rather than a meaningful measure of the pet’s health. Achieving an ideal body condition score and/or an improvement in a health improvement is a much more useful goal for most pets. For example, if a dog with arthritis that could barely walk around the block before weight loss is able to regain her ability to go on walks and play without as much pain, the program has been very successful regardless of the end weight. End weights can also be somewhat misleading as patients convert pounds of fat into pounds of muscle.

Weight loss plans end when the goals of the program have been achieved. That may in fact be a goal weight, but often that may be a body condition score or an improvement in a health problem. Regardless of the specific end point, success should be celebrated, and the habits and behavioral changes that achieved the weight loss should be retained for the rest of the pet’s life.