At present, obesity is the most common health issue in humans. It is an emerging health problem in the pet population also. Obesity is a condition where an excessive amount of fat is accumulated in the body. In obese pets, the ribs, spine, and pelvic bones are not well defined. The chest, spine, and base of the tail are covered with fat. It not only harms the health of companion animals but also decreases their life expectancy.
What causes obesity?
Multiple factors are responsible for causing obesity in companion animals. It usually results from an imbalance between excessive calorie intake and inadequate energy burned due to less physical activity. This results in a state of energy imbalance and ultimately leads to obesity. Factors that are involved in the development of obesity in companion animals are listed below-
1. Dietary factors
Pets have more chances of developing obesity if they are kept on high-caloric food with less physical activity. The metabolic rate and physical activity are directly affecting energy metabolism. Major hormones associated with obesity are leptin and adiponectin. Appetite is regulated by the leptin hormone, which is secreted from fat cells. This hormone helps in regulating body weight by signaling satiety to the hypothalamus and thus reduces dietary intake and fat storage. It regulates the energy balance between food intake and energy expenditure. Therefore, the hunger response does not trigger when the body does not need calories. The level of leptin is related to fat mass. The fluctuation of leptin from normal results in uncontrolled feeding, which results in the development of obesity. Obese pets have high circulating leptin levels, but their hypothalamus does not get a satiety signal to stop feeding. It is called “leptin resistance”.
Adiponectin is an adipose tissue-derived hormone and is present at very high concentrations in the bloodstream. Adiponectin is reciprocal to leptin release. Its concentration is more in lean individuals but lowest in obese people. Moreover, feeding in dogs and cats are relatable to the bond and behavior of their owner. They feed their pet many meals and snacks regardless of their caloric value.
2. Metabolic and endocrine disorder
Some metabolic and endocrine disorders e.g. hypothyroidism, hyperadrenocorticism, diabetes mellitus, hypopituitarism, hyperlipidemia, and glucose intolerance play a significant role in the causation of obesity.
Indoor housing is also a risk factor for the development of obesity in dogs and cats. It leads to a sedentary lifestyle with a lack of exercise resulting in obesity. Behavioral factors also play a role in obesity development in cats. Many cat owners misinterpret the behavior of their cat with eating. Whenever their cats initiate contact with owners, they often offer food by assuming that they are hungry but they are not. Eventually, the cat learns that by initiating contact, food is offered. This behavior results in obesity.
Neutering is a significant risk factor for obesity in both male and female companion animals. The hormonal alterations that occur due to spaying or castration in dogs influence appetite, glucose tolerance, and lipid metabolism. Several studies depicted that after neutering, there is a decrease in the concentration of sex hormones leading to a 25-30 % decrease in metabolic rate resulting in obesity.
5. Genetic factors
Pet owners should know the genetic characteristics of breeds of dogs and cats. Some breeds tend to develop obesity i.e. Labrador Retriever, Boxer, Cairn Terrier, Shetland sheepdog, Basset hound, Cavalier King Charles spaniel, Cocker spaniel, long-haired Dachshund, Beagle, and Scottish Terrier breeds of dogs and Domestic Shorthair breed of cat. Moreover, obesity tends to increase with age in dogs and cats as the metabolic rate decreases as the age advances. It is demonstrated that the Greyhounds breed of dogs does not develop obesity.
Some drugs like glucocorticoids and anticonvulsant drugs lead to polyphagia, which results in obesity. Corticosteroid therapy especially dexamethasone increases leptin concentrations in dogs, which may influence the appetite.
Complications associated with obesity in companion animals
Obesity in companion animals is associated with orthopedic disease, diabetes mellitus, cardiac diseases, respiratory disease, urinary disorders, dystocia, tumors, dermatological diseases, exercise intolerance, heat intolerance, decreased life expectancy, and anesthetic complications.
1. Orthopedic disorders
Obesity is an important risk factor for orthopedic diseases in companion animals, especially in dogs. It is a predisposing factor in humeral condylar fractures, cranial cruciate ligament rupture, and intervertebral disc disease in cocker spaniels breed of dog. Increased body weight in obese dogs exerts excessive pressure on the joints and ligaments, leading to degenerative effects and lameness. It is reported that the reduction in body weight leads to improvement in the degree of lameness in dogs. Several studies revealed the association between obesity and the occurrence of osteoarthritis.
2. Diabetes mellitus
In the present scenario, diabetes mellitus is the most common endocrine disorder in humans. But the incidence of diabetes mellitus is increasing in dogs and cats day by day. Obesity is a significant risk factor for diabetes mellitus in dogs and cats by causing insulin resistance and hyperinsulinemia. Obesity results in peripheral insulin resistance in dogs, which is similar to type I diabetes mellitus in humans. This may be due to a lower level of adiponectin in the obese dog. Cat most often suffer from diabetes mellitus, which resembles type II diabetes mellitus in humans.
3. Respiratory and cardiac disorders
Excessive accumulation of fat in obese dogs hampers the movement of the diaphragm during respiration. Obesity is reported as a significant risk factor for the development of tracheal collapse in small dogs. it can exacerbate laryngeal paralysis and brachycephalic airway obstruction syndrome.
Obesity causes an increase in heart rate, cardiac output, arterial pressure, and plasma volume. The association of obesity with portal vein thrombosis and myocardial hypoxia is demonstrated.
4. Reproductive disorder
Obesity is the cause of infertility, ovulation dysfunction, fetal growth disorders, and abortion in some dogs. In obese dogs risk of dystocia during parturition is high due to the accumulation of fatty tissues in and around the birth canal. Fat deposited around the pelvis reduces the elasticity of pelvic ligaments.
5. Urinary disorders
Obese dogs suffer from painful micturition which occurs due to caudal displacements of the urinary bladder by increased retroperitoneal fat. This excess fat puts pressure on the abdomen, causes increased urethral mobility, and more pressure on the urinary bladder results in urinary incontinence. Association of obesity with urethral sphincter mechanism incompetence is reported. A higher incidence of developing calcium oxalate urolithiasis is reported in some obese dogs.
In some dogs, obesity is reported to be associated with mammary carcinoma. Obese dogs have an increased risk of developing transitional cell carcinoma of the bladder.
7. Dermatologic disorders
There is an increased risk of certain dermatologic disorders (e.g. alopecia and epidermal scaling) and pressure sores in obese animals. Diffuse scale is commonly observed in cats due to a reduced ability to groom efficiently.
How to manage obesity?
Early recognition of obesity and correcting the obesity when it is present are crucial for the health of companion animals. No specific drugs or medications for the correction of obesity in dogs and cats. Therapeutic management for obesity in companion animals includes dietary management with increasing physical activity for weight reduction. Correction of obesity subsequently prevents all other complications or issues related to adiposity.
1) Dietary management
Starvation is not recommended for reducing weight as it causes excessive loss of protein from the body. For reduction of weight, caloric intake should be restricted. Protein and micronutrients should be supplemented in the diet. Along with fat and energy restriction, L-carnitine and conjugated linoleic acid (CLA) in the diet helps in weight loss. Supplementing L-carnitine @50–300 ppm in the diet improves nitrogen retention, increases lean mass, and reduces fatty tissue from the body. It acts by enhancing fatty acid oxidation and makes the availability of energy for protein synthesis during times of need. Conjugated linoleic acid is derived from linoleic acid and its antiadipogenic effect has been demonstrated by some researchers. But at present, data on the use of CLA as an antiobesity agent are contradictory.
Increasing physical activity along with dietary therapy promotes fat loss and may assist in lean tissue preservation. Exercise for dogs includes lead walking, swimming, hydrotherapy, and treadmills. Cats should be involved in play activities like fishing rod toys and feeding toys. Furthermore, it is essential to supervise and monitor the whole weight reduction regimen. It is time-consuming and needs expertise. Monitoring of weight is important even after the ideal body weight has been achieved.
How to prevent obesity? Obesity is a preventable disease. The ideal body weight of the pet must be estimated and accordingly energy requirements should be met. A body condition score is a useful method to determine and monitor a pet’s weight. Many pet owners do not realize that obesity is a medical health issue and causes risk for their pet’s life. Therefore, counselling of pet owners about obesity and its negative effects on pet’s health is recommended. In this way, the health of pets is promoted and further complications that are associated with obesity can be prevented.