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European Veterinary Conference Voorjaarsdagen Amsterdam, Netherlands 24 - 26 April, 2008
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Reprinted in IVIS with the permission of the Conference Organizers
Gastro-enterology Reprinted in IVIS with the permission of the Organizers
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Scientific Proceedings: Companion Animals Programme
Obesity management: conventional therapy
A.J. German BVSc, PhD, CertSAM, DipECVIM-CA, MRCVS, Department of Veterinary Clinical Sciences, University of Liverpool, UK,
[email protected] Introduction Obesity is defined as an accumulation of excessive amounts of adipose tissue in the body; the disease predisposes to a variety of diseases including diabetes mellitus, osteoarthritis, and cardiorespiratory diseases. In most animals, obesity is the result of a simple imbalance between energy intake and energy expenditure. This lecture will discuss current thoughts on both conventional management of obesity in dogs and cats.
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Causes of obesity Obesity can arise secondary to a number of diseases including endocrinopathies (e.g. hypothyroidism and hyperadrenocorticism in dogs), drugs (e.g. polyphagia caused by glucocorticoids and anti-convulsant drugs), and rare genetic disorders (in humans), although the main reason for development of obesity is an imbalance in the ‘energy balance equation’. In this respect, either excessive dietary intake or inadequate energy utilisation can lead to a state of positive energy balance, leading to increased white adipose tissue deposition. Numerous
Gastro-enterology Reprinted in IVIS with the permission of the Organizers
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Scientific Proceedings: Companion Animals Programme
factors may influence the relative ease with which weight is gained, and these include genetics, age, neuter status, amount of physical activity, calorific content of the diet. Overview of treatment of obesity in dogs and cats In humans, current therapeutic options for obesity include dietary management, exercise, psychological and behavioural modification, drug therapy, and surgery. Temporary weight loss, by liposuction, does not have an equivalent effect and does not affect metabolic risk. Liposuction removes only subcutaneous fat, which carries little metabolic risk, and energy intake is unaffected; therefore, body weight will rise again to achieve energy balance. Bariatric surgery is the most successful method of weight loss in humans, and average weight loss is ~23%. Various approaches are described including gastric banding and the roux-en-y procedure. This success comes at a cost, since the complication rate is high (including peri-operative mortality, short-term and long-term consequences. For companion animals, it is not considered ethically justifiable to manage obesity through surgical means. However, pharmaceuticals have recently become available for treatment of obesity in dogs (see separate talk). Such therapies may prove to be a useful addition to the therapeutic options in the near future, although it should be stressed that, for any therapy (pharmaceutical, dietary etc) to have long-term success, it is ESSENTIAL to modify owner and animal behaviour. Unless steps are taken to change feeding habits and exercise patterns, weight regain will occur. This rebound effect is a well-known phenomenon of any weight loss program. Therefore, to achieve longterm success weight loss is only the start rather than the end of therapy. Conventional options for weight management include dietary therapy and behavioural modifications; such strategies are likely to remain for dogs and, given that no pharmaceutical agents have yet been approved for cats, this approach will remain the mainstay of therapy in this species. Dietary management The weight reduction protocol should always be tailored for the individual patient. Although complete starvation leads to rapid (~7%/week) weight loss, it has the disadvantages of causing excessive protein (and thus lean body mass) loss and requiring hospitalisation to monitor. Further, adverse effects on body system function have been reported (e.g. cardiovascular function is compromised). Therefore, it is preferable to use purpose-formulated diets, and most formulated rations are restricted in fat and calories, whilst being
supplemented in protein and micronutrients. Protein supplementation is important since, although weight loss is not more rapid, the amount of lean tissue lost is minimised. Supplementation of micronutrients ensures that deficiency states do not arise. Other diet components that have been employed in weight management include L-carnitine supplementation (to maintain lean mass), conjugated linoleic acid, and use of high-fibre diets (to provide satiety; see below). L-carnitine is an amino acid which is synthesised de novo, from lysine and methionine, in the presence of ascorbate. In one double-blind placebo-controlled study, orally-administered L-carnitine in a moist weight loss diet for cats lead to more rapid weight loss than placebo. Dietary supplementation of L-carnitine improves nitrogen retention and body composition in favour of increased lean mass and decreased fat mass. Incorporation of L-carnitine, at a level of 50-300 parts per million, in weight reduction diets has been shown to maintain lean tissue 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. Conjugated linoleic acid (CLA) is a family of fatty acid isomers derived from linoleic acid. Studies in experimental animals have suggested an anti-adipogenic effect; the mechanism of action is not known, but possibilities include inhibition of stearoyl-CoA desaturase activity which limits synthesis of monounsaturated fatty acids for triglyceride synthesis, and suppression of elongation and desaturation of fatty acids into long-chain fatty acids. Currently, date are conflicting data on the benefit of CLA as an anti-obesity agent in humans and cats, with the most recent data suggesting lack of a significant effect. Therefore, more information is required before its use can be recommended, although a recent metaanalysis of human data suggested a modest beneficial effect in favour of weight loss. A major hurdle to conventional weight loss programs is the fact that energy restriction causes hunger, leading to increased begging and scavenging activity. This puts increased strain on the owner-animal bond, causing owner non-compliance or complete withdrawal from the program. Therefore, developing strategies to improve satiety would greatly assist in case management. The results of many human studies have shown that absorption of macronutrients is lower following consumption of high-protein foods than after consumption of foods with a high carbohydrate or fat content. The amino acids from the digestion of proteins are absorbed slowly and the main path of their metabolism is gluconeogenesis.
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Gastro-enterology Reprinted in IVIS with the permission of the Organizers
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Scientific Proceedings: Companion Animals Programme
Therefore, proteins are sources of glucose that induce little insulin secretion and delay the appearance of hypoglycaemia (which contributes to the feeling of hunger). The satiety effect of proteins is variable, because speed of digestion varies amongst different proteins, and different amino acids induce the secretion of insulin to varying degrees. Dietary fibre may also increase satiety, due to gastric distension which causes cholecystokinin release and a subsequent slowing of gastric emptying. Under certain conditions in humans, dietary fibre has been shown to exert a satiety effect, although some studies have failed to detect significant reduction in appetite. There are similar discrepancies in canine studies with some, but not all studies suggesting effects on satiety. Apparent inconsistencies are likely the result of differing investigative methods and of the dose and type of fibre used. In recent studies in colony dogs, three different diets (HPHF, high protein [103g/1000Kcal] high fibre [60g/1000Kcal]; HP, high protein [104g/1000Kcal] moderate fibre [35g/1000Kcal]; HF, moderate protein [86g/1000Kcal] high fibre [87g/1000Kcal],) designed for weight loss were assessed for their satiety effect. Voluntary food intake was measured in five sequential crossover studies, and palatability was assessed with taste tests. Short- (food offered for 15min every hour for 4h) and medium-term (food offered 3h after the first meal) satiety was best for the HPHF diet. Voluntary food intake at the second meal (fed 3h after a restricted meal of 25% of daily metabolic energy requirements) was significantly lower than the first meal for the HPHF diet, but not the HP or HF diets. The HPHF and HP diets had equivalent palatability, and both were more palatable than the HF diet. These studies suggest that diets supplemented in both protein and fibre have the greatest satiating effect, and may improve compliance with conventional weight loss programs. Lifestyle management Increasing physical activity is a useful adjunct to dietary therapy during weight management; studies in humans suggest that increasing activity promotes fat loss, whilst preserving lean tissue during weight loss. The exact program must be tailored to the individual, and take account of any concurrent medical concerns. Suitable exercise strategies in dogs include lead walking, swimming, hydrotherapy, and treadmills. Exercise in cats can be encouraged by increasing play activity, using cat toys (e.g. fishing rod toys), motorised units and feeding toys. Cats can also be encouraged to ‘work’ for their food by moving the food bowl between rooms prior to feeding, or by the use of feeding toys. Activity monitors (accelerometers, pedometers) have recently been validated for dogs, and may help to provide a more objective assessment of activity during weight loss
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programs in the future. Monitoring weight loss In addition to the above strategies, it is essential that the whole weight reduction regime be closely supervised. This is labour-intensive, requires some degree or expertise and training in owner counselling, and often requires a dedicated member of staff. Nevertheless, in the author’s opinion, correct monitoring is the single most important component to the weight loss strategy. A recent study has demonstrated that weight loss is more successful if an organised strategy is followed with regular weigh-in sessions. It is essential to continue to monitor body weight after ideal weight has been achieved to ensure that weight that was lost is not regained; as with humans, a rebound effect has been demonstrated after weight loss in dogs. This has been seen in ~50% of dogs that successfully lose weight. Review of conventional weight loss programmes Weight loss programs in experimental studies Conventional weight loss regimes, involving dietary caloric energy restriction, are highly successful in obese colony dogs. Rates of weight loss of 1.3-2.6%/week have been achieved with caloric allocations of 50-87%. The most important factors that influence response include breed, gender and neuter status. Previous work with colony dogs has demonstrated breed differences in the level of energy restriction required to achieve the same rate of weight loss, with Labrador retrievers requiring a greater level of restriction than beagles. Age, sex, neuter status and activity level have also been shown to be of importance. The main factor that has been shown to affect the rate of weight loss is the level of caloric energy restriction. Nevertheless, whilst the level of protein does not appear to affect rate of weight loss, the proportion of lean tissue loss is lower on a high-protein diet, compared with a diet of moderate protein content. Weight loss in client-owned dogs In a recent study at the University of Liverpool, success of weight loss was reviewed in 19 client-owned dogs, with naturally-occurring obesity. A conventional weight loss program was used which employed caloric energy restriction, using a high-protein/moderate fibre diet, and behavioural modification strategies. Body composition was quantified by dual-energy X-ray absorptiometry before and after weight loss. Mean percentage weight lost was 18% (range=6-29%). The mean rate of weight loss was 0.85%/week (range=0.35-1.56%) and this was negatively correlated with the overall duration of the program. Mean energy allocation required to achieve weight loss was 52% of mean energy requirement at target weight (MERTW, range=42-70%; maintenance
Gastro-enterology Reprinted in IVIS with the permission of the Organizers
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Scientific Proceedings: Companion Animals Programme
MER=132xBW0.73 Kcal/day); allocation was lower in neutered vs. entire dogs. Further, significant dietary non-compliance was reported (mean 0.9% MERTW; range=0.0-7.9%). The ratio of the mean composition of the tissue lost was 84:15:1 (fat:lean:bone mineral); the proportion of lean tissue lost was positively correlated with the overall percentage of weight lost. The results would suggest that conventional programs lead to safe weight loss in dogs, but that marked caloric energy restriction is required, and the rate of loss is slower than in experimental studies. Summary Successful weight loss in dogs and cats requires dedi-
cation and commitment. Conventional weight loss strategies involving diet and exercise can be highly successful in both dogs and cats, whilst pharmaceutical agents provide another means to achieve target weight. Successful weight loss involves not only achieving an ideal body weight, but maintaining it subsequently. In the author’s opinion, preventing the known and predictable rebound effect seen with any weight loss strategy, requires changes in both owner and pet behaviour, and is the key factor in true success. References are available on request
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