Although Body Condition Scoring (BCS) is becoming a standard veterinary tool for judging the physical status of pets, many pet owners and veterinarians are more comfortable with weight as a measure of health. Owners of animals on weight loss programs tend to be more compliant if they have a target weight for their pet rather than a target BCS.
This makes sense. Despite the medical field embracement of the Body Mass Index (BMI), weight targets are still the standard in most popular human weight loss programs. Research by veterinary nutritionist, Dr. Angela Witzel at the University of Tennessee has created a means to calculate ideal weight from BCS information.
BCS and Body Fat Percentage
Dr. Witzel and her group compared BCS scores (both the 5-point chart and 9-point scales for dogs and cats) to the gold standard for the determination of percentage of body fat, dual-energy X-ray absorptiometry or DEXA. They found the following correlations of BCS scores and percent body fat:
(Click image to see larger view)
Calculating Ideal Weight for Cats and Dogs
With the above information we can estimate the ideal weight of an overweight pet.
A 100 lb dog with a BCS of 5 or 9 (depending on the scale used).
This dog is 40% overweight so its lean body weight would be 60% of its present weight.
100 lbs X .6 = 60 lbs
60 lbs represents a dog with no fat, which is not healthy. From the information above, ideal animals should have about 20% body fat, or 80% lean weight.
60 lbs/.8 = 75 lbs
The ideal weight for our dog is 75 lbs. More correctly, the ideal weight is between 70-80 lbs because the ideal body fat ranges from 15-24%, or 76-85% lean body mass.
This calculation is not accurate for grossly obese pets. Such pets exceed the standard BCS scoring so the correlation of percentage of body fat to BCS score is difficult to define. Typically the percent of body fat is underestimated, which has a profound effect on designing a weight loss program for these pets.
Using the Ideal Body Weight Chart for Your Pet
Determination of a pet’s ideal weight allows for more accurate feeding guidelines. This is particularly true for pets on weight loss programs. In order to lose weight, a pet must be fed fewer calories than the amount that would support their ideal weight. Equipped with an ideal weight plan, your veterinarian can calculate the normal caloric requirements and then decrease by a percentage the amount that is appropriate and safe for the individual pet.
Having a defined target weight gives owners a goal and helps increase their compliance to the weight loss recommendations. In the bigger picture, these calculations are estimates. Also, metabolic changes occur during dieting or calorie restrictions that seek to preserve fat, so pets often encounter plateaus of no weight loss or short periods of weight regain. That is why regular monitoring is required for any weight loss program. Adjustment to caloric intake is the norm, not the exception. They don’t make an autopilot for weight loss.
I hope this post was interesting as well as informative. I hope you will calculate your pet’s ideal weight and seek veterinary help if it exceeds ideal. You can literally add years to your pet’s life by keeping him at an ideal weight. My motto is, “Score a 4 and live some more!”
Dr. Ken Tudor
To see the full charts, click the links below.