Small Animal Obesity: Effective Control, Management and Care

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SMALL ANIMAL OBESITY: EFFECTIVE CONTROL, MANAGEMENT AND CARE

Author : Catherine F Le Bars

Categories : Vets

Date : February 23, 2009

Catherine F Le Bars explains how the battle of the bulge and the medical implications specific to certain species need a careful approach to both owner and pet

OBESITY is one of the most common nutrition-related conditions in companion animals in the industrialised world, and has a proven association with the development of several disease conditions and reduced longevity.

Since weight gain occurs when daily energy intake exceeds energy expenditure, the prevention of obesity requires strict attention to the animal’s nutrition throughout its life. Obesity treatment may be complicated by many factors, and successful management of the condition relies on rigorous owner compliance.

Estimates from around the world put the incidence of obesity in dogs and cats at up to 40 per cent, and a number of risk factors have been implicated in its development. These include breed, age, gender, neutering, medication (anti-convulsants, glucocorticoids and contraceptives), lifestyle and exercise, co-existing disease (diabetes mellitus, hypothyroidism, hyperadrenocorticism) and diet.

The regulation of food intake is dependent on a complex balance of long-term and shortterm signals to the brain, which are aimed at controlling the fat mass of the animal. When this balance is disrupted, the animal consumes energy above its requirements and gains weight. There are three recognised stages of weight gain:

1 / 10 • A “static ” pre-obesity stage, whereby energy intake is increased but bodyweight remains the same.

• A “dynamic” phase, in which the animal gains weight, primarily in the form of fat.

• A “static” phase, in which food intake may be reduced as the balance between energy intake and expenditure is re-established. However, the weight remains high because the metabolic rate is relatively low.

Obesity has significant implications for the individual’s health, increasing the risk of osteoarthritis, diabetes mellitus, dystocia, hyperlipidaemia, reduced immune function, pancreatitis, cardiorespiratory complaints and alterations in thyroid function. Obese canines display poor exercise tolerance and may be at greater risk of developing urinary incontinence, mammary tumours and dermatopathies. Obese cats are prone to the development of lower urinary tract disease and hepatic lipidosis, while rabbits are at greater risk from gastrointestinal disorders and fly strike.

Measuring obesity

Companion animals may be classed as overweight when their bodyweight exceeds an estimated optimal weight by more than 15 per cent, and obese when they are more than 30 per cent above optimal.

However, the assessment of optimal bodyweight is often subjective, since reliable measures used in humans – such as the body mass index (BMI) – have not been established for general use in cats and dogs.

The proper measurement or assessment of obesity relies on the division of body composition into fat mass (FM) and lean body mass (LBM). Several tests are available, which may vary considerably in precision, accuracy, practicality, invasiveness and cost.

In a research environment, tools used for assessment of body composition include: chemical analysis, total body water measurement, electrical conductance, dual-energy x-ray absorptiometry (DXA), subcutaneous and/or visceral ultrasonography, CT and MRI. However, these tests are costly, invasive and require a level of technical skill or equipment not available in many veterinary practices.

The easiest and most widely used procedures in a clinical setting are measurements of bodyweight and morphometry (measurement of form). The latter assesses body condition by measuring different parameters. The three main approaches in morphometry are: measurements of skin fold thickness, body condition scoring and dimensional evaluations.

2 / 10 Skin fold thickness has been widely used in humans, with various equations to determine body fat percentages, but such measurements are unreliable in dogs and cats because their skin detaches more easily from subcutaneous fat.

Body condition scoring (BCS) is subjective but precise (it produces repeatable results), and uses a five or nine-point scheme to estimate subcutaneous and abdominal fat relative to superficial muscles. It relies on the visual assessment and palpation of areas such as the ribcage, waist and dorsal spinous processes to give an overall assessment of body condition. However, it does not give quantitative measurements of fat mass and lean muscle mass.

Dimensional evaluations have been used in cats and dogs to produce schemes similar to the human BMI. These techniques provide a more objective result than BCS, but do not extrapolate well between breeds. Studies demonstrate a good correlation between the lengths of limbs and trunk with LBM, and girth with both LBM and FM. Combining these measurements has generated equations that can be used to quantify different body components.

In dogs, the pelvic circumference and distance from stifle to hock has been used to predict body fat percentages. In cats, the body circumference is measured at the ninth rib instead. Reference charts are becoming available, and may provide resistant owners with proof that their pets are obese.

Management

Management of obesity centres on reducing the caloric intake and increasing energy expenditure where possible. In theory, this simply requires modifications in diet and exercise, and yet implementing a successful weight loss programme often proves a challenge in veterinary practice.

Before a weight loss programme can be formulated, the animal’s current diet and lifestyle should be fully evaluated, and any potential pet or owner constraints identified. Since owner compliance, often for the remainder of the animal’s life, is of crucial importance, individual programmes must find a way to work within these constraints. Many owners have concerns about food palatability, and often misinterpret their pet’s behaviour as hunger. Additionally, there is the common and often deeply rooted belief that “food means love” to overcome.

A detailed history, physical examination and careful client questioning are key to the successful management of these patients. In many cases, both owner and animal behavioural issues are partially responsible for the development of obesity in the first place, and neglecting these issues will result in poor owner compliance and treatment failure.

Dietary therapy aims to reduce energy intake and should be tailored to the individual, taking into account concurrent disease (allergies, renal impairment, GI disease etc) and the degree of weight loss required. An appropriate diet will reduce adipose tissue while preserving lean muscle mass. In

3 / 10 cats and dogs, this can be achieved by feeding a properly formulated weight reduction diet, which is restricted in fat and energy, while being supplemented in proteins and micronutrients. The addition of fibre is of questionable value.

Obese cats should be mana ged carefully because severe caloric restrictions may lead to hepatic lipidosis in a very short period. A safe regime restricts caloric intake to 60 to 75 per cent of the estimated requirements for its ideal bodyweight (IBW).

This approximates to 60kcal/ kg of IBW daily, and should result in weight loss of one to 1.5 per cent per week, although variations in an individual’s requirements may require further food intake adjustment.

Studies investigating the manipulation of dietary macronutrients in obese cats at risk from glucose intolerance and diabetes indicate that a high-protein and/or low-carbohydrate diet may increase satiety and facilitate weight loss. The inclu sion of fermentable fibre may be of benefit, as products of its metabolism increase the secretion of insulin from pancreatic islets. Carbohydrates should account for less than 25 per cent of caloric content, and studies indicate there may be some benefit to feeding carbohydrates from sources such as sorghum and barley, rather than rice, in the prevention or management of obesity-induced diabetes.

Following the restriction of caloric intake, the next step is to increase caloric expenditure in the form of a sensible exercise programme.

Exercise must be appropriate for the individual’s level of mobility, recognising that only minimal exercise or low-impact activities may be achievable in severely obese or arthritic animals.

Cats can be encouraged to exercise by increasing play activity with the use of toys. Moving feed bowls between rooms prior to mealtimes and the use of feeding toys can also help encourage cats to “work” for their food. One study has demonstrated that actively playing with obese cats for 10 minutes a day was as effective as restricting energy intake. As mentioned before, the successful management of obesity relies on strict owner compliance. Behavioural issues arising from the owner and pet bond must be addressed, particularly the “food means love” strategy practised by so many owners. In certain cases, where the animal appears to beg relentlessly for food, specialist behavioural advice may be required. Other methods of weight control used in humans, such as surgery, have not been practised widely in veterinary medicine, and are still considered ethically questionable.

Pharmaceutical intervention has become possible with the introduction of two drugs – dirlotapide and mitratapide. Both are licensed for canine obesity management in the UK. These drugs should be used as part of a weight management programme, and it should be noted that these drugs are not to be used in cats under any circumstances.

4 / 10 Although these drugs may produce good weight loss, appetite will return on the cessation of treatment and further weightcontrol strategies are required to prevent weight gain.

Both dirlotapide and mitratapide are microsomal triglyceride transfer protein inhibitors, and work at the level of the intestinal epithelium by decreasing lipid absorption, and reducing appetite (most probably by the release of a “satiety” signal). The latter is considered to be of most benefit, as it may reduce negative behaviours, such begging and scavenging, which are often responsible for poor owner compliance.

Dirlotapide is licensed for continuous use for periods of up to 12 months. Initial treatment is at a low dose, which is doubled after a fortnight and then adjusted monthly according to measured weight loss. Significant weight loss is achievable during this period. Mitratapide is dosed for two three- week periods, separated by a fortnight. Dietary adjustments are made during the two-week break from medication. The manufacturers state that this protocol can result in a reduction in bodyweight of five to 10 per cent.

Successful and safe weight reduction using these drugs relies on feeding a balanced diet, to ensure the animal does not develop any deficiencies. The fat content should be restricted, but diets too low in fat may limit the efficacy of either drug. Currently, a fat level of 10 per cent is recommended. Additionally, a good-quality protein should be fed at a minimum of 100g/1,000kcal.

Both medications are well tolerated, but sporadic vomiting may occur in up to 20 per cent of treated animals. Other side effects include lethargy, anorexia and diarrhoea. Many of these signs occur early in the treatment and resolve or improve with time.

Some patients exhibit mild elevations in liver enzymes, although the significance of such changes is, as yet, unknown. Occasionally, owners perceive the reduced appetite as a negative, reporting that their pets display less affection towards them than previously.

Nutraceuticals, such as linoleic acid and diacylglycerol, have been used with limited success, but controlled studies have yet to confirm their role in weight-reduction strategies. L-carnitine supplements have been shown to assist the transport of long-chain fatty acids into mitochondria, thereby preserving lean muscle mass. Dietary supplementation with vitamin A has shown promise in obese cats, particularly those with insulin resistance.

Obesity in companion animals mirrors the worldwide trend of rising human obesity, and has been identified as a risk factor in the development of many diseases. Effective management of these patients requires the establishment of weight reduction protocols tailored to the individual, including dietary and lifestyle modifications, and occasionally pharmaceutical intervention.

• References are available on request to the editor.

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Some estimates put the incidence of obesity in dogs and cats at 22 to 40 per cent, and a number of risk factors have been implicated in its development.

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A successful weight loss programme must consider the animal’s current diet and lifestyle, and any potential pet or owner constraints.

8 / 10 9 / 10

Obesity has significant implications for the individual’s health, increasing the risk of diseases such as osteoarthritis, diabetes mellitus and pancreatitis.

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