August 2, 2019
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.
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.
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
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
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 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.
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.
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:
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.
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.
Some pets have a slower metabolic rate than others, and factors such as a low activity level, orthopedic disease, and spay or neuter status can impact how many calories a cat or dog needs each day. It is often helpful to go back to the diet history after calculating energy requirements and comparing current intake to the calculated energy requirement for weight loss. If the pet’s current intake is higher than the calculated amount, the veterinary team can proceed with the next step. If the pet is currently eating less than the calculated amount he or she needs for weight loss, it can be helpful to revisit the diet history. For canine patients, it can be beneficial to check thyroid hormone levels. It also can be helpful to consult a board certified veterinary nutritionist when the pet is eating less than the calculated amount for weight loss.
Animals with excess body weight should ideally be placed on a therapeutic weight loss diet. These formulas are nutrient-dense, meaning there is a higher concentration of protein, essential fatty acids, vitamins, and minerals per kilocalorie when compared to a maintenance diet. Therapeutic weight loss diets also are lower in energy density, allowing the owner to feed the pet a larger volume of food. Other options include therapeutic “moderate calorie” diets designed for obese-prone patients with other health conditions, as well as over-the-counter weight management diets. These are typically used when the patient has concurrent disease or when the patient is not extremely overweight. Most obese patients require a therapeutic weight loss diet for safe and successful weight loss. The goal is to provide adequate nutrition while restricting calories for weight loss.
Treats can be included in a successful weight loss plan, but should be considered when calculating total caloric intake. Additionally, they should make up no more than five to 10 percent of total calories. Most owners are unaware of the high calorie content in treats, which can make up a significant percentage of calorie intake. Reducing the number of treats, as well as modifying treat type, is usually necessary when designing a weight loss plan.
Patients should be weighed every two weeks during a weight loss plan to allow for safe weight loss at a rate of 0.5 to two percent of body weight per week. If the patient is losing weight too quickly or too slowly, the caloric intake should be adjusted in five to 10 percent increments. Treat intake should be adjusted as well. Based on the rule of thumb that weight loss should occur at 0.5 to two percent of starting body weight per week, the owner can be given a time frame in which weight loss would ideally occur. This can help provide them a sense of perspective and a realistic timeline.
In addition to feeding an appropriate diet for weight loss at an appropriate amount, monitoring patients is essential for success and will also improve client compliance. Once target weight is achieved and the pet is in ideal body condition, the patient should receive an average of five to 10 percent more calories than what was necessary to achieve weight loss to maintain ideal body weight.
This systematic step-by-step approach helps manage many patients, but each pet must be assessed on an individual basis and will require a nutritional plan targeted to its specific needs. Use your nutritional assessment to help discover your patient’s requirements, to understand the owner’s feeding methods and practices, and to help develop the most effective weight loss plans for your patients.
1 Weeth LP. Other risks/possible benefits of obesity. Vet Clin North Am Small Anim Pract 2016; 46: 843-853.
2 Association of Pet Obesity Prevention 2018 Pet Obesity Survey Results, https://petobesityprevention.org/2018, accessed 5/12/19.
3 Toll PW, Yamka RM, Schoenherr WD, Hand MS. Obesity. In: Small Animal Clinical Nutrition, 5th Edition, eds. Hand MS et al. Topeka, KS: Mark Morris Institute; 2010.
4 Larsen JA, Villaverde C. Scope of the problem and perception by owners and veterinarians. Vet Clin North Am Small Anim Pract 2016; 46: 761-772.
5 German AJ, Holden SL, Wiseman-Orr ML, et al. Quality of life is reduced in obese dogs but improves after successful weight loss. Vet J 2012; 192: 428-434.
6 Kealy RD, Lawler DF, Ballam JM, et al. Effects of diet restriction and life span and age-related changes in dogs. J Am Vet Med Assoc 2002; 220: 1315-1320.
7 Salt C, Morris PJ, Wilson D, et al. Association between life span and body condition score in neutered client-owned dogs. J Vet Intern Med 2019; 33: 89-99.
8 Churchill J, Ward E. Communicating with pet owners about obesity: roles of the veterinary health care team. Vet Clin North Am Small Anim Pract 2016; 46: 899-911.
9 Baldwin K, Bartges J, Buffington T, et al. AAHA nutritional assessment guidelines for dogs and cats. J Am Anim Hosp Assoc 2010; 46: 285-296.
10 Laflamme D. Companion Animals Symposium: obesity in dogs and cats: What is wrong with being fat? J Anim Sci 2012; 90: 1653–62.
Catherine Lenox, DVM, DACVN, is a nutritionist with Royal Canin USA. She also teaches online nutrition continuing education through the Veterinary Information Network (VIN). Dr. Lenox can be reached at firstname.lastname@example.org.
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