Obesity is defined as excess body weight that may contribute to impaired health and body function.1 Survey data suggest more than half of the cats and dogs in the U.S. are overweight or obese,2 making obesity the most common nutritional disease in companion animals. Pets with up to 20 percent excess body weight are considered overweight (corresponding to a body condition score [BCS] of 6/9 and 7/9), while pets with more than 20 percent excess body weight are considered obese (BCS 8/9 and 9/9).3 Obesity can result from animal factors, such as breed or spay/neuter status, or from considerations related to their owners, such as diet choice or feeding methods.4 As such, it can be challenging to discuss obesity with pet owners and to design and implement weight loss plans. This article discusses obesity and offers a step-by-step approach to canine and feline weight loss. Using this system for appropriate patients can help standardize your care for the overweight or obese pet.
Why obesity is a problem
Obesity is not a concern simply because it's common. On the contrary, it presents health risks. Overweight and obese animals are at risk for a number of health conditions, including diabetes mellitus, cardiac and respiratory disease, degenerative joint disease, inflammatory diseases, and neoplasia.1 Obesity is also associated with decreased quality of life and shorter lifespan in dogs.5-7 Obese animals are more difficult to examine (e.g. abdominal palpation can be further challenging) and excess body fat can interfere with diagnostic tests, such as radiography and ultrasound.
Designing a weight loss plan for a cat or dog
For most overweight and obese patients, a standardized approach helps improve success. However, this methodology should not be applied to certain patients. Pets that have systemic illness requiring a specific veterinary therapeutic diet (e.g. formulas for chronic kidney disease), a diet formulated for growth (e.g. puppies and kittens), and those with severe illness (e.g. congestive heart failure or neoplasia) should be treated with special care, even when obese. For those patients, consulting with a board certified veterinary nutritionist (acvn.org) may be needed.
A weight loss plan for the uncomplicated overweight or obese patient should include these seven steps:
1) Communicate with the owner about a weight loss plan
2) Perform a nutritional assessment
3) Estimate ideal body weight
4) Estimate energy requirements
5) Compare current caloric intake to estimated energy requirements
6) Select a diet and feeding plan
7) Monitor and follow up
Communicating with the pet owner about obesity
The communication piece is essential to a successful weight loss plan, but it is often the most difficult part of the process. Some pet owners do not realize their pet is overweight, and it can be a sensitive subject to broach. When the pet owner is overweight themselves, it can become even more challenging to initiate the conversation. Focusing on the health effects of excess weight is the most important thing, as it puts the needs of the cat or dog first. Involving the entire veterinary team when communicating with pet owners regarding pet obesity can be useful and can help improve compliance.8
Diagnosis of obesity and nutritional assessment
A thorough nutritional assessment, including body weight, body condition score (BCS), muscle condition score (MCS), and a thorough diet history is necessary, in addition to a standard medical history and physical examination.9
Body condition score
Body condition scoring provides an estimate of body fat mass. There are two body condition scoring systems: the nine-point scale and the five-point scale. Both range from emaciated (1/9 or 1/5) to obese (9/9 or 5/5). Ideal BCS is considered 4 to 5/9 or 2.5 to 3/5. Animals above ideal body condition are considered overweight or obese.
Muscle condition score
MCS estimates lean muscle mass independent of BCS. In addition to obtaining a BCS on each patient, muscle condition can be scored on a scale of normal, mildly decreased, moderately decreased, or severely decreased. A patient with a severe decrease in muscle mass can still be obese, and in these particular cases, body condition scoring may be more difficult because the animal will seem "bonier" due to lost muscle mass.
Diet history
A thorough diet history provides insight into both the animal's caloric intake and the owner's feeding practices. Asking open-ended questions can frequently help the veterinary team discover more valuable information about what the pet is eating.
Diet history components include:
- The pet's main diet type, along with amount, frequency, and duration of feeding and how it is measured
- All treat types, as well as amount and frequency
- Human foods/table scraps with type, amount, and frequency
- Food for medication administration
- Food for training
- Access to other pets' food
- Any other food the pet can access indoors or outdoors
- Dietary supplements
- Flavored medications
- Toothpaste
Estimating body weight
Each body condition score point on the nine-point BCS scale is equivalent to approximately 10 percent of body weight.10 Using that guideline, estimated ideal body weight can be calculated using the following formula:
Ideal body weight = Current body weight/division factor (see Table 1)
Estimated ideal weight is a starting point for a weight loss plan. In all cases, the patient will need to be monitored to determine if the ideal body weight calculation is appropriate. Asking the owner for information regarding previous weight also can provide insight into the pet's ideal body weight.
Estimating energy requirements
While there are multiple formulas used to calculate resting energy requirements (RER), the exponential formula below is most accurate for all animals. This can be done using body weight in kilograms using:
RER (kcal/day) = 70 x (BWkg)0.75
Multiplying RER x 1.0 for dogs and RER x 0.8 for cats using ideal body weight calculations can help determine energy requirements for weight loss, although these equations should be used for overweight and obese animals without additional health complications. Energy requirements also can be determined by obtaining a thorough diet history of the patient and calculating current caloric intake, then decreasing intake by 20 percent. Sometimes, one method works better than another, depending on the patient and other factors.
