Prevention of Obesity in Dogs And Cats
The number of pets that are overweight or obese has reached epidemic proportions in the USA and other industrialized countries.
For example, just over 35% of adult cats in the USA are overweight or obese. As veterinarians, we need to be proactive on
focusing on obesity prevention. Wellness visits are the ideal time to regularly re-assess body weight history and body condition
score. The benefits of maintaining a pet in lean body condition, and the health risks (and expense) that can accompany obesity
are important owner education topics. The veterinary visit for spaying/neutering is an important, but often neglected, opportunity
to reassess diet type and feeding management and make appropriate awareness of obesity issues to clients. Studies in cats
have shown that neutering decreases metabolic rate by 25-33%. Neutered animals, however, usually have increased fat mass.
When energy expenditure is expressed on a lean mass basis, no difference in metabolic rate is noted between neutered and entire
individuals. Alternative explanations for the effect of neutering on obesity is an alteration in feeding behavior leading
to increased food intake and decreased activity, without a corresponding decrease in energy intake.
Middle-aged neutered male cats and middle-aged spayed female dogs are at highest risk of becoming obese. Some purebred dogs
are at higher risk of becoming obese'; these include Shetland Sheepdogs, Golden Retrievers, Dachshunds, Cocker Spaniels, Labrador
Retrievers, Dalmatians, and Rottweilers. Manx cats are more likely to become obese than other purebred cats. Not surprisingly,
low activity level increases risk for weight gain in both species; in cats, apartment dwelling is associated with a higher
risk. Obesity in dogs is associated with the number of meals and snacks fed, the feeding of table scraps, and the dog's presence
when its owners prepared or ate their own meal.
The first step in managing obesity is getting owners to recognize it as a problem. A weight reduction protocol must be tailored
for the individual patient, with consideration given to the following components: initial assessment of health status and
any disease conditions present concurrently with obesity, caloric intake, diet selection, exercise, behavioral modification,
pharmacologic intervention, follow up, and weight maintenance after optimal weight is achieved. A successful weight loss program
requires some combination of reduction in caloric intake (owner compliance) and an increase in physical activity. A pharmacologic
aid to decrease caloric intake can also be considered as part of the program for dogs.
Results from the emerging field of nutragenomics show differences in gene expression profiles in lean and obese pets. Nutragenomics
has been used to develop diets that alter gene expression in obese pets to more closely resemble the gene expression profiles
in lean pets. Furthermore, preliminary data suggest that weight loss can correct the systemic effects of obesity. Microarray
analysis indicates that the gene expression of adipocytes and lymphocytes from obese dogs and cats, compared to lean pets,
show a down regulation of genes such as PPAR-gamma, uncoupling protein-2, carnitine O-palmitoyltransferase 1 A and acyl-CoA
synthetase that are important in the beta-oxidation of fatty acids (Yamka, R.M., K.G. Friesen, et al. The effects of weight
loss on gene expression in dogs. 2008 ACVIM Meeting, San Antonio). Down-regulation of these genes may explain why obese animals
are fat-storing instead of fat-burning. In addition, adipose tissue from obese pets shows down-regulation of genes associated
with glucose metabolism, such as pyruvate dehydrogenase kinase-4 and glucose-6-phosphatase. These observations may explain
why obese animals become insulin resistant and have increased circulating glucose, insulin, IGF-1 and inflammation.
Although energy restriction can be achieved by feeding the pet's regular food, this approach has the disadvantage of causing
excessive loss of lean body mass as well as having the potential to deplete essential micronutrients. Therefore, it is strongly
recommended to use purpose-formulated weight loss diets, which generally are restricted in fat and energy, but are higher
than adult maintenance diets in protein and micronutrients. Enhanced amounts of protein are very important because the amount
of lean tissue lost is minimized even though the weight loss is not more rapid.
Additional dietary factors that may be of benefit for weight loss include L-carnitine supplementation, high-fiber diets, and
conjugated linoleic acid (CLA). L-Carnitine is an amino acid that is synthesized de novo in the liver and kidneys from lysine and methionine in the presence of ascorbate. Dietary supplementation of L-carnitine
improves nitrogen retention, increasing lean mass and reducing fat mass. Incorporation of L-carnitine at a level of 50–300
ppm in weight reduction diets has been shown to reduce lean tissue loss during weight loss. Possible mechanisms for this protective
effect on lean tissue include enhancing fatty acid oxidation and energy availability for protein synthesis during times of
need. There is also controversy concerning the effect of fiber satiety; some reports suggested that feeding up to 12–16% of
dry matter as dietary fiber has no effect, whereas other work demonstrated appetite suppression when 21% of the diet was consumed
as diet ary fiber. Data is conflicting on the possible benefit of CLA in weight loss diets. Studies in experimental animals
suggested that it has an antiadipogenic effect, but data on the use of CLA as an antiobesity agent in humans and cats are
conflicting, with the most recent data suggesting lack of a significant effect.