Feline Obesity Clinical Recognition and Management by zhouwenjuan


									3 CE
CREDITS   CE Article 1

                                                                                                                                                      Courtesy of Carol Adams, Lone Oak Veterinary Clinic
   Feline Obesity:
   Clinical Recognition and Management
   ❯❯ Debra L. Zoran, DVM, MS,             Abstract: Obesity is one of the most common clinical problems in cats presenting to veterinary
      PhD, DACVIMa                         practitioners. Because it is a risk factor for other conditions, such as diabetes mellitus and hepatic
      Texas A&M University
                                           lipidosis, it not only increases the morbidity of affected cats but may also shorten their life span. In
                                           cats, a body weight of greater than 20% over the ideal weight of the animal is generally accepted
                                           as obese. The goal of this article is to help all members of the health care team understand how to
                                           prevent the development of obesity in young cats and, when confronted with an obese adult cat,
                                           how to develop a safe and effective weight-loss program.

   At a Glance
                                                      epending on the study cited, the           Preventing Obesity
                                                      number of obese or overweight              The commonly stated reason for devel-
     Preventing Obesity                               cats in Western societies ranges           opment of obesity is that an animal
     Page 284                              from 15% to 35%, with practitioners estimat-          is consuming more energy than it is
     Steps in a Weight-Loss                ing even higher numbers in some areas.1–5             expending.12 This energy imbalance can
     Program for an Obese Cat              A body weight of greater than 20% over                be due to excessive dietary intake of calo-
     Page 286                              the ideal weight of the animal is generally           ries or a reduction in energy expenditure.
     Clinical Evaluation                   accepted as obese for cats, which means               However, obesity is not just a simple mat-
     of Obese Cats                         that a 4-kg (9-lb) cat that gains 1 kg (2 lb) is      ter of intake or output. Many other fac-
     Page 287                              considered obese. Obesity in cats not only            tors that can influence or control appetite,
     Methods of Assessing                  is a cosmetic problem but also increases              metabolism, and homeostasis, including
     Body Condition                        the risk of development of diabetes6 and              genetic predisposition, sex, neuter status,
     Page 288                              hepatic lipidosis7 and is associated with             and hormonal disturbances, may play sig-
                                           increased incidences of many other condi-             nificant roles in the development of obe-
     Obesity and Diet
     Page 289                              tions, such as lower urinary tract disease            sity.5,8,12 As a result, it is important to make
                                           and osteoarthritis.8 Presuming that obesity           a concentrated effort to recognize risk fac-
     Creating a Treatment Plan             in cats is similar to that in dogs and humans,        tors, monitor young and middle-aged cats
     Page 291
                                           this condition will also shorten the life             carefully to detect excess weight gain early,
                                           span of affected cats.8–11 Considering the            promote the importance of obesity pre-
                                           number of cats already affected and the               vention and the health benefits of weight
                                           great difficulty in getting a 12-kg (25-lb) cat       control from the first veterinary visit, and
     Dr. Zoran discloses that she has
                                           to weigh 4.5 kg (10 lb) again, it is clear that       be actively involved in body assessment
   received financial support from
   Nestlé Purina Petcare and Pfizer        the situation demands veterinarians’ full             (weight and body condition score [BCS])
   Animal Health.                          attention.                                            of all cats at every visit. In other words,

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                                                                                                                                    Feline Obesity CE

obesity prevention must start early, and the              Even when owners measure the amount of
veterinary team is essential to recognition, food they give their cats, feeding recommen-
early intervention, and success.                      dations based on the label recommendations
    There is now ample evidence that neutering for a particular food or traditional maintenance
is an important risk factor for obesity in male energy calculations are likely to result in sig-
and female cats.13–19 For some time, it has been nificant overfeeding. These recommendations
recognized that many cats have significant are based on feeding trials in intact, young,
weight gain after neutering or during their ado- active cats—not neutered, indoor (sedentary)
lescent years, but most clinicians believed this cats—and as a result, they are approximately
was due entirely to the type or amount of food 30% higher than most housecats need. While
fed. However, several recent studies13–18 have the appropriate number of calories proposed
shown that multiple hormonal changes that sig- in the veterinary literature for the maintenance
nificantly affect feline metabolism immediately energy requirement in cats ranges from 20 to
follow removal of the gonads.a These changes 100 kcal metabolizable energy (ME)/kg/day,
affect food intake and energy metabolism and multiple papers have suggested that 70(BWkg)0.75
result in an increase in body fat mass that is represents the resting energy requirement and
almost inevitable unless appropriate measures 94 to 125(BWkg)0.75 the accepted range for the
to limit intake are taken immediately.14–19           maintenance energy requirement for cats.
                                                          However, in 2006, the National Research
Controlling Food Intake                               Council recommended maintenance amounts
Because gonadectomy is now recognized as a of 130(BWkg)0.40 for obese cats and 100(BW)0.67
risk factor for obesity,13–18 the key factor for pre- for lean cats,21 and several recent studies of neu-
vention of obesity in neutered animals appears tered cats have shown that feeding cats typical
to be careful control of intake immediately after maintenance amounts of food results in weight                                      QuickNotes
neutering (e.g., no free-choice feeding) and and (more importantly) fat mass gain.22 Kienzle
close monitoring of body weight and BCS to and colleagues23 analyzed the caloric needs in                                            Obesity is a com-
allow adjustments in intake if needed.14,16,18 As a                                                                                  mon, serious medi-
                                                       Box 1
rule of thumb, intake recommendations based                                                                                          cal problem in cats.
on commercial food labels should be reduced              Free-Choice Feeding and
by 30% for neutered animals to account for the
hormonal changes resulting in reduced energy             Feline Health
needs.14,16,18 Several studies have evaluated the
role of different amounts of dietary components          Free-choice feeding of dry food affects
(e.g., fat, carbohydrates) in the development of         overall feline health in many ways, including:
obesity after neutering, but the key factors that           Inadequate water intake, which can lead to an
result in increase in body weight are gonadec-              increased risk of constipation and urolithsa,b
tomy and free-choice access to food.17,19 Free-
                                                            Learned preference for dry food, which
choice access to dry food is not an appropriate
                                                            may make it difficult to change to a
method of feeding for many cats—particularly
                                                            therapeutic canned dietc
indoor, neutered, inactive cats—for many rea-
sons (Box 1). The most important with regard to             Inability of owners to monitor the amount
obesity is the risk of overfeeding (or overeating),         of food being eaten, which may lead them
which even in very small amounts can exceed                 to miss subtle signs of illnessd
appropriate caloric intake and result in weight
gain. Further, due to the feline preference (and,        a
                                                           Seefeldt SL, Chapman TE. Body content and turnover in cats fed
                                                         dry and canned rations. Am J Vet Res 1979;40:183-185.
when eating small meals such as mice, physi-             b
                                                           Finco DR, Adams DD, Crowell WA, et al. Food and water intake
ologic need) for eating multiple meals a day, it         and urine composition in cats: influence of continuous versus
is best to provide cats’ caloric requirements in         periodic feeding. Am J Vet Res 1986;47:1638-1642.

two to four meals/day.    20                             c
                                                           Horowitz D, Soulard Y, Junien-Castagna A. The feeding behavior
                                                                 of the cat. In: Pibot P, Biourge V, Elliott D, eds. Encyclopedia
                                                                 of Feline Clinical Nutrition. Aniwa SAS, Aimargues, France;
  For an overview of some of the metabolic changes related       d
                                                                   Houpt KA. Feeding and drinking behavior problems. Vet Clin
to obesity, see the companion article on CompendiumVet.          North Am Small Anim Pract 1991;21:281-298.

                                                      CompendiumVet.com | June 2009 | Compendium: Continuing Education for Veterinarians®            285
CE Feline Obesity
                            colony cats and reported that neutered females               for cats—one that will be extremely difficult to
                            required 100(BW kg ) 0.40 and neutered males                 achieve in cats being fed a calorie-dense (high-
                            required 120(BWkg ) 0.40 to maintain ideal body              fat) food or allowed free access to dry food.
                            condition. In two other feeding studies,24,b inves-
                            tigators determined that neutered cats consum-               Increasing Exercise
                            ing more than 50 to 60(BWkg)0.67 gained weight               Like many people, indoor cats are sedentary,
                            and underwent a change in BCS from ideal to                  which has detrimental effects on their physiologic
                            obese in just 3 months.                                      and psychologic health and well-being. Therefore,
                               In simple terms, an intake of 30% less than               increasing activity and energy expenditure are
                            maintenance requirements means that most                     very important aspects of weight management
                            average-sized, indoor, neutered cats weighing                in indoor cats. However, it is not easy to induce
                            4 to 5 kg (9 to 11 lb) need to eat less than 200             cats to exercise. Lifestyle alteration is, then, one
                            kcal/day, and many may need even less than                   of the most important additions to any program
                            180 kcal/day to maintain lean body condition                 of obesity prevention or management.25
                            (Box 2). This is a significantly smaller amount of               Exercise is a key factor in health for several
                            food than is often recommended and represents                reasons: (1) it helps maintain and strengthen
                            a critical change in feeding recommendations                 lean muscle tissues, (2) it promotes cardiovas-
                                                                                         cular health, (3) it provides mental stimula-
 QuickNotes                  b
                               Bauer JE. Texas A&M University. Personal communication.   tion and improves overall quality of life, (4)
 Indoor, neutered            2009.                                                       it increases energy expenditure and fat oxida-
 cats are at greatest
                              Box 2
 risk of becoming
 obese if their intake          Steps in a Weight-Loss Program for an Obese Cat19,23,38,a
 is not carefully lim-
 ited soon after they           1. Determine ideal body weight: Set a                        If the cat is considered to be 60% above its
 achieve adult size.               target goal for weight loss.                              ideal weight, the ideal BW would be 6.25 kg
                                      A record of the cat’s ideal weight at an               (13.75 lb).
                                      earlier age is the most accurate guide.
                                                                                          2. Determine the amount to feed: Energy
                                      If you have no previous record of ideal                allocation.
                                      weight, you must estimate an ideal from
                                      the current weight. This can be done by                  If possible, determine how much the cat is
                                      using the body condition score (BCS):                    currently consuming. This may be difficult
                                      On a 9-point scale, each point above a 5                 if the cat is being fed free-choice or lives
                                      represents a 10% to 15% increase in                      in a multicat household without careful
                                      body weight (BW).                                        observation of intake.
                                      Using this approach, a cat weighing                      If the amount is known, an intake reduction
                                      10 kg (22 lb) and having a BCS of 9/9                    of 20% to 40% from the calculated
                                      is 40% to 60% above its ideal weight.                    maintenance requirements for a cat of ideal
                                      Using an equation with both BW and                       body condition is a good starting point for
                                      the percentage over BCS can provide an                   weight loss. The diet fed should contain
                                      estimate of ideal BW:                                    >45% metabolizable energy of protein and
                                                                                               be low in fat.
                                                100% (normal BCS)
                               Ideal BW =                             × current weight         The current National Research Council
                                            100% + % above normal BCS
                                                                                               recommendations for maintenance require-
                                                                                               ments in lean and obese cats are as follows:
                                   If the cat is considered to be 40% above its              Lean cat: 100 kcal(BW)0.67 or 60 kcal/kg/
                                   ideal weight, the ideal BW is calculated as               day. For a 4-kg cat, this equals 240 kcal/day
                                   follows:                                                  (4 kg × 60 kcal/kg/day = 240 kcal/day). Note
                                            100%                                             that many indoor, neutered cats, even if they
                                                 × 10 kg = 7.1 kg (15 lb)                    are lean, need 20% to 30% less than this
                                                                                             amount, or less than 200 kcal/day.

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                                                                                                                             Feline Obesity CE

tion, and (5) it increases the metabolic rate.26 If    for indoor cats to increase their muscle mass
feasible, protected outdoor activity should be         and reduce their risk of obesity.
encouraged, as it is a great stimulus for play or
exercise activity. Cats that are unable to engage      Clinical Evaluation of Obese Cats
in outdoor hunting or play behavior need other        The first step in identifying and correcting obe-
opportunities to fulfill their physiologic needs      sity is recognizing it. Obviously, it is not diffi-
for climbing, balancing, scratching, and exer-        cult to recognize a severely obese animal, but
cise.25,27,28 These requirements can be met in        the veterinarian’s goal is to recognize changes
many ways and can be tailored to the cat and          in body weight and condition early so that cor-
its situation. Toys may work well for some cats,      rections in diet, intake, and exercise can be ini-
cat trees or play stations are excellent for oth-     tiated to prevent progression to obesity, with
ers, and some cats respond well to interactive        all of its associated hormonal changes and
toys that reward them with food. Clients do           comorbid conditions.
not need to turn mice loose in their house to             For assessment purposes, body composition
encourage activity or play, but they do have to       is typically separated into fat mass and fat-free
engage their cats to create play opportunities.       mass (FFM). The FFM is the largest, heaviest
The most important message about exercise             portion and includes protein (muscle mass),
that veterinarians should give cat owners is          minerals (bones), and water (intracellular and
that play and activity are essential components       extracellular). Measuring or assessing the FFM                          QuickNotes
of a healthy feline lifestyle and are necessary       provides essential information about an animal’s
                                                                                                                              Play and activity are
                                                                                                                              essential compo-
                                                                                                                              nents of a healthy
                                                                                                                              feline lifestyle
                                                                                                                              and are necessary
   Obese cat: 130 kcal(BW)0.40 or 37 kcal/kg/              are essential to continued success.                                for indoor cats
   day. For an 8-kg cat, this equals 296 kcal/             Adjustments in the weight-loss program are                         to increase their
   day (8 kg × 37 kcal/kg/day = 296 kcal/day).             based on results. If the cat is not losing weight                  muscle mass and
    However, to achieve weight loss in an                  at a rate of 1% per week, the amount of food                       reduce their risk of
    obese cat, its intake must be decreased                intake should be decreased by 5% to 10%.
    to 60% of the maintenance requirements:                                                                                   obesity.
                                                           Weight loss should be monitored frequently
    0.60 × 296 = 178 kcal/day. In practice, this           (every 2 to 4 weeks) and, to avoid discrep-
    can be rounded up to 180 kcal/day.                     ancies, always using the same scale.
    Some obese cats may need to consume                    Other recommended monitoring tools in-
    as little as 20 to 30 kcal/kg/day to achieve           clude BCS, morphometric measurements,
    weight loss. This amount of food is very               and photographs.
    small, and the greatest concern is to
    maintain adequate protein intake.                      As with any chronic disease, weight
                                                           management requires a good veterinarian–
                                                           client–patient relationship to achieve
3. Monitor the weight-loss program and                     optimal care and results.
   make adjustments.                                       It may be helpful to give owners an
    The goal of weight loss is 1% to 2% of                 estimated time line for weight loss so
    BW per week. At this rate, the cat is less             that they have realistic expectations for
    likely to lose lean muscle mass or develop             results. In general, for a cat to have a 30%
    hepatic lipidosis.                                     decrease in BW, it takes approximately
    Typically, cats lose weight more quickly at            12 months if the cat is losing 0.5%/week,
    the start of the program, but metabolic and            7 months if the cat is losing 1%/week,
    physiologic responses to weight loss result            or 4 months if the cat is losing 2%/week.
    in significant slowing or even cessation of        a
                                                        Hashimoto M, Funaba M, Abe M, et al. Dietary protein levels affect
    weight loss over a short period of time. Thus,     water intake and urinary excretion of magnesium and phosphorus,
    monitoring progress and making adjustments         in laboratory cats. Exp Anim 1995;44:29-35.

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CE Feline Obesity
                             metabolic and physiologic status.29 Cats in thin         be performed on an awake cat. They include
                             body condition with loss of muscle mass are              BCS, morphometric measurements, and body
                             known to have higher morbidity and mortality             mass index (BMI).29 Tools used in clinical or
                             and should be evaluated to determine the cause           basic research also exist; detailed informa-
                             of the loss.30 By contrast, obesity is the accumu-       tion on these techniques has been published
                             lation of body fat or an increase in the fat mass.       elsewhere. 8,29,31
                             In most cats, obesity represents an increase in
                             fat mass that causes increases in body weight            Body Condition Scoring
                             and changes in body composition.                         BCS is perhaps the most widely accepted and
                                 Measurement of body weight is the simplest           well-known technique for assessing increased
                             technique for determining increased fat mass.            fat mass.31–33 The two most common scoring
                             However, there are two main concerns with                systems are the 5-point system (in which a
                             using only body weight monitoring: (1) mea-              score of 3 is ideal) and the 9-point system
                             surement of body weight alone does not dis-              (in which 5 is considered ideal).8,32 However,
                             tinguish the loss of FFM from the loss of fat            because half points are often used in the
                             mass, and (2) scales are notoriously inaccurate          5-point system, resulting in a total of 9 catego-
                             or variable—measurements made on different               ries, the systems are essentially identical, and
                             scales can vary significantly. When weighing             clinical use is based on preference.
                             cats, it is important to use a reliable, well-              One disadvantage of using BCS to assess
                             maintained scale intended for small animals              fat mass is that physical palpation cannot dis-
                             (pediatric scales are excellent) and to use the          tinguish loss of FFM from gain of fat mass. So
                             same scale for all weight tracking to minimize           although BCS can provide a subjective assess-
                             variability and maximize accuracy. However, to           ment of an increase or decrease in fat mass in
 QuickNotes                  better assess body condition, most nutritionists         obese patients, it is not helpful in overall body
                             recommend that techniques for specific assess-           condition assessment of FFM. For example, a cat
 Clinicians should           ment of fat mass be incorporated in the physi-           with diabetes may be obese but have also lost
 familiarize them-           cal examination in addition to measuring body            muscle mass due to the lack of insulin result-
 selves with at least        weight. In general, the techniques available to          ing in muscle wasting. Simple assessment of BCS
 one of the clinical         clinical practitioners (Box 3) are easy to use,          by palpation cannot accurately distinguish these
 techniques for              require no special instrumentation, and can              changes. Another disadvantage of BCS is its
 assessment of body                                                                   lack of repeatability in inexperienced observ-
                              Box 3                                                   ers. However, for estimating body fat mass in
 composition and
 use it daily.                  Methods of Assessing Body                             a clinical setting, BCS is an important tool. It
                                                                                      provides owners with tangible information
                                Condition8                                            about their pets and, when used repeatedly so
                                                                                      that familiarity and comfort are achieved, can
                                Clinically useful methods                             provide highly reproducible results.8,32,33
                                 Serial body weight
                                                                                      Morphometry and Body Mass Index
                                 Body condition score
                                                                                      Morphometric measurements and determina-
                                 Morphometric measurements                            tion of BMI are also easy to use in a clinical
                                 Bioelectric impedance                                setting; however, they are less well known and
                                 Body mass index                                      require more time. Morphometric analysis uses
                                Research methods                                      measured parameters to provide an estimate of
                                 Dual energy x-ray absorptiometry (DEXA)              body composition. The simplest measurements
                                                                                      are dimensional evaluations, whereby a tape
                                 Dilution/isotope techniques
                                                                                      measure is used to obtain specific dimensions
                                 Ultrasonography, computed tomography,                of the animal. In general, length measurements
                                 or magnetic resonance imaging
                                                                                      of the head, thorax, and limbs correlate well
                                 Electrical conductance                               with lean body mass,34 while circumference
                                 Chemical analysis                                    measurements (truncal/ribcage) correlate with
                                 Neutron activation analysis                          fat mass.35 By using a measurement of lean
                                                                                      body mass (leg index) with a measurement of

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                                                                                                              Feline Obesity CE

fat mass (ribcage circumference) in the follow-               acids and fatty acids that they are unable to
ing equation, BMI can be predicted28:                         synthesize from other food sources as omnivo-
                                                                                       rous species do.38 The
                       1.5 (ribcage circumference [cm] – leg index measurement [cm])   most commonly used
  Feline BMI (% fat) =
                                                     9                                 foods for cats are dry,
                                                                                       extruded diets. These
In this equation, the ribcage circumference is foods meet the minimum requirements of the
measured at the ninth cranial rib, and the leg National Research Council and are nutritionally
index is the distance from the patella to the complete and balanced, readily available, easy
calcaneal tuber of one hindlimb.36                            to use and store, and quite palatable. However,
    Other morphometric measurements of body they bear little resemblance to a diet of a natu-
composition use specific tools to assess fat ral carnivore. Therefore, the distinctive nutri-
composition, such as ultrasonography (this ent requirements of cats should be taken into
technique has not been validated in cats) or account when designing a weight-loss or main-
bioelectric impedance analysis (BIA). In BIA, tenance diet.
the conductance of an applied electric current
in the patient is measured and used to calculate Protein
body composition.29,35,37 Because body fluids As obligate carnivores, cats use protein as an
and electrolytes are responsible for the highest energy source even when other energy sources                    QuickNotes
conductance and adipose tissue is dehydrated, such as fat or carbohydrates are available.38
increased adipose tissue results in lower con- However, most researchers have focused on
                                                                                                                 Successful weight
ductance and greater impedance.29 Although fat and carbohydrate energy sources as having                         loss in cats requires
several BIA systems exist, none are widely the primary roles in the prevention and man-                          preservation of lean
available, and there are few reports of their agement of obesity. While it is critically impor-                  muscle tissue and
use in cats. BIA can be affected by electrode tant to reduce caloric intake in cats to achieve                   concurrent loss of
position, hydration status, consumption of food successful weight loss, this approach has over-                  fat mass, which is
or water, physical activity, conductance of the looked the important role of protein in feline                   best achieved using
examination table, and other variables.37 Thus, metabolism. Hoenig and colleagues39 showed
                                                                                                                 high-protein (>45%
further evaluation of this technique is needed that cats consuming high-protein diets (>45%
before it can be recommended for routine use ME) had increased energy metabolism, higher
                                                                                                                 ME), low-energy
in the assessment of fat mass in cats.                        fat oxidation, and improved glucose tolerance,     diets.
                          ***                                 while cats consuming high-carbohydrate diets
    Clinicians should familiarize themselves with had lower energy metabolism, required fewer
at least one of the clinical techniques for assess- calories to meet their needs, and gained fat
ment of body composition and use it daily so mass. Others40–43 have also shown that in obese
that it becomes not only a normal part of every cats, diets containing high levels of protein
physical examination but also a more reliable result in greater loss of fat mass and improved
and repeatable tool for assessing fat mass. preservation of muscle mass. This is important
Routine use of BCS also shows clients that their because muscle mass is a major determinant
veterinarian considers body condition assess- of metabolism. Muscle mass loss provokes a
ment to be an important part of their cat’s “starvation” response as the body seeks to pre-
physical examination and health evaluation. serve itself either through energy metabolism
Perception is reality: owners need to know that changes or increased intake. Therefore, loss of
obesity is important not only from what veteri- muscle mass increases the likelihood of weight
narians say but also from what we do.                         regain, and, particularly in cats, maintaining
                                                              muscle mass may be a key to successful weight
Obesity and Diet                                              loss.44 Research has shown that even cats con-
Diet must be considered in any prevention or suming protein at 45% ME lost some muscle
treatment plan for feline obesity. Unlike most mass during diet restriction. This finding sug-
domestic species, cats are true carnivores. They gests that >45% ME of protein may be needed
must consume animal flesh and fat to meet their during weight loss due to the severe restric-
nutritional needs, or their diets must be supple- tion of intake necessary to achieve reduction
mented appropriately with the necessary amino in calories and loss of weight.40,41

                                                 CompendiumVet.com | June 2009 | Compendium: Continuing Education for Veterinarians®   289
CE Feline Obesity
                                 Obese cats appear to adapt to lower-                  drates; on the contrary, they can digest, absorb,
                              protein, higher-carbohydrate diets; however,             and use them quite well. Nevertheless, the type
                              obese cats on high-protein diets have not only           of carbohydrate is important, as there are signif-
                              improved insulin sensitivity but also greater            icant differences in glycemia, postprandial glu-
                              energy and fat metabolism, resulting in great            cose levels, insulin secretion, and food intake
                              loss of fat mass during calorie restriction and          between normal-weight and obese cats.47,48
                              weight loss.39 Increased protein intake may be
                              particularly important in cats after weight loss,        Fat
                              as research also shows that energy expendi-              The role of dietary fat is also very important
                              ture remains decreased.44                                in feline obesity, as fat provides the greatest
                                 In summary, high protein levels are essen-            amount of energy per gram of diet. As a result,
                              tial for preservation of lean body mass dur-             there are a number of commercially available
                              ing calorie restriction and weight loss in obese         low-fat feline diets for calorie control. Further,
                              cats and are important for increasing insulin            several recent studies show that controlling
                              sensitivity, thereby preventing further devel-           calories from fat in weight-loss programs
                              opment of glucose intolerance. In addition,              is essential to achieving successful weight
     to lEarn MorE            high-protein diets (>45% protein ME) allow a             loss.19,21 Nevertheless, dietary fat has many
                              more optimum metabolic status in lean cats.              roles in metabolism beyond being a power-
                                                                                       ful source of energy, and there are key differ-
                              Carbohydrates                                            ences in feline requirements for fat that must
                              While protein is a very important component of           be considered when choosing a diet.
                              the feline diet, it is only one part. Carbohydrates         As carnivores, cats require additional sup-
                              serve two major purposes: as an energy source            plementation of fatty acids (especially arachi-
 Your gateway to
 trusted resources for        (simple carbohydrates, such as starches) or as           donic acid) and fat-soluble vitamins in their
 your veterinary team:        dietary fiber (complex carbohydrates). The role          diet that normally would come from the fat
                              of fiber is discussed in a separate section below.       stores of prey. Also, fat is a major palatabil-
  Web exclusives                  Carbohydrates are a major part of most dry and       ity enhancer, and cats often reject diets with
  Articles                    some canned commercial feline and canine diets           too little fat or in which the fat is oxidized.
  News                        due to issues of processing, preservation, and cost.      Box 4
  Video                       The digestibility and glycemic index of dietary car-
  VLS online store            bohydrate varies by source: highly digestible car-          Major Metabolic/Anatomic
                              bohydrates include cooked white rice and potato;            Differences in Feline
    and so much more!
                              less digestible sources include complex grains (e.g.,       Carbohydrate Handling
                              barley, wheat, whole corn). Carbohydrates in high-
                              quality commercial pet foods are generally highly           Compared With Omnivoresa
                              digestible and provide a readily available energy
                              source. If the pet is active and needs energy, car-             Lack of a sweet taste receptor and gene
                              bohydrates are used efficiently; however, if the                for sweet taste
                              pet is sedentary, any carbohydrates that are not                Lack of salivary amylase (enzyme that
                              used for energy are stored as fat.                              initiates digestion of starches)
                                  The amount and type of carbohydrate in the                  Low levels (5% to 10%) of intestinal
                              feline diet are of considerable importance for                  amylase and intestinal disaccharidases
                              several reasons: (1) cats’ ability to handle dietary            Minimally functioning levels of hepatic
                              carbohydrate loads are very different from those                glucokinase (inducible enzyme that affects
                                                                                              glucose uptake)
                              of omnivores38,45 (Box 4); (2) because cats use
                              protein for energy, even when excess energy                     Minimally functioning levels of hepatic
                                                                                              glycogen synthetase (enzyme that
                              is available in their diet, sedentary indoor cats
                                                                                              converts glucose to glycogen)
                              often do not use the carbohydrate energy pres-
                                                                                              Lack of fructokinase and ability to
                              ent in a diet38,46; and (3) high-carbohydrate diets
                                                                                              metabolize fructose sugars
                              result in a reduced resting energy metabolism,
                              so cats must consume less food to maintain                  a
                                                                                           Zoran DL. The unique nutritional needs of the cat. In: Ettinger
                              appropriate body weight.39                                  S, Feldman E, eds. Textbook of Veterinary Internal Medicine. 7th
                                                                                          ed. 2009, in press.
                                  However, cats are not unable to use carbohy-

 290    Compendium: Continuing Education for Veterinarians® | June 2009 | CompendiumVet.com
                                                                                                            Feline Obesity CE

However, while reducing fat is an important           energy metabolism. Ideally, weight-loss diets
method of controlling calories in feline diets,       should contain protein levels >45% ME and
there are no studies in cats showing the ideal        be low in fat and carbohydrates. The number
amount of fat in the diet. And as with protein        of dry diet choices that meet this profile is
and carbohydrates, it is essential to consider        extremely small, primarily because most high-
the whole: diets for weight loss in cats should       protein, low-carbohydrate dry foods are for-
ideally be higher in protein (at least >45% ME),      mulated as either diabetic or kitten diets and
lower in fat (to control calories) but contain-       thus contain a large number of calories due
ing enough essential fatty acids to meet feline       to a high fat content. For example, a typical
requirements, and lower in carbohydrates (to          dry diabetic or kitten food contains 500 to 600
prevent reduction in energy metabolism and            kcal/cup of food. As a result, it is extremely
conversion of excess carbohydrate to fat).            difficult to feed an appropriate amount to a
                                                      cat that requires weight loss, which, in an
Fiber                                                 obese cat, may be as low as 130 to 150 kcal/
The final dietary component to consider in            day. In this scenario, the amount of the high-
weight-loss diets is fiber. Most weight-loss diets    calorie diabetic dry food fed at a meal will be
add insoluble or mixed sources of fiber, such         small (< 1/8 cup twice daily)—likely too small
as cellulose or beet pulp. Dietary fibers have        to achieve any sense of “fullness” and result-
been used in weight-loss diets for many years         ing in annoying begging behavior that makes              QuickNotes
because of their ability to dilute calories and       owner compliance with feeding recommenda-
                                                                                                               Weight loss in
provide bulk to the diet so that larger volumes       tions very difficult.
of food can be eaten during energy restriction.          This point cannot be overstated: too many
                                                                                                               obese cats is dif-
Fiber aids in glycemic and weight control by          calories of any kind, including protein calories,        ficult and requires
promoting slow, sustained absorption of glu-          will cause weight gain or failure to lose weight.        appropriate dietary
cose (and other nutrients) from the gastroin-         Thus, at this time, the best commercial diets            intervention to pre-
testinal tract and by increasing the speed of         for achieving a high-protein, low-carbohydrate,          serve muscle mass,
passage of food through the small intestine.          low- to moderate-fat profile that can provide            careful control of
However, this effect, while beneficial for weight     reasonable portion sizes are canned cat foods.           intake, and frequent
loss, results in reduced digestibility of protein49   For example, a typical diabetic (high-protein/           monitoring to make
and may have other untoward effects, such             low-carbohydrate) canned diet contains 165 to
                                                                                                               adjustments as
as increased fecal volume, constipation, food         190 kcal/5.5-oz can. Thus, when the target for
refusal, and dry skin.50 As a result, many own-       caloric intake is 180 kcal or less, it can be easier
ers and cats do not tolerate diets with moder-        to achieve the high protein necessary to pre-
ate to high levels of dietary fiber (>15% dry         serve muscle mass in a portion-controlled diet
matter). No studies demonstrate an optimum            with these foods. However, canned foods can
amount or type of dietary fiber for use in cat        also be high in carbohydrate or low in protein
foods for any purpose; however, a moderate            or have poor-quality ingredients, resulting in
amount (5% to 12% dry matter) of mixed fiber          ineffective or unhealthy weight loss. One size
may be best.50                                        does not fit all in cat foods, and careful read-
   If a moderate- to high-fiber diet is cho-          ing of the label can help determine the protein,
sen, the effects on protein digestibility must        carbohydrate, and fat levels, which is the start
be considered and an appropriate amount of            of the process.
protein added to the food to prevent a reduc-
tion in protein availability. As with any dietary     Creating a Treatment Plan
strategy, increased fiber in the diet should          Successful weight loss in an obese cat requires
not be considered a “cure-all” for weight loss,       patience, setting goals, frequent monitoring
but it can be included as part of the overall         and readjustment of strategy, and an under-
approach to controlling caloric intake.               standing that reversing obesity is a challenge
                                                      similar to the management of any chronic
Choosing a Weight-loss Diet                           medical condition. Persistence and diligence
Healthy weight loss requires loss of adipose          are essential. The key is to set a target calorie
tissue along with maintenance of lean body            intake, weigh the cat monthly, and adjust the
mass, which is an important arbiter of basal          amount of food based on weight loss. While

                                               CompendiumVet.com | June 2009 | Compendium: Continuing Education for Veterinarians®   291
CE Feline Obesity
                                           the most appropriate rate of weight loss is                                   tered cats are at risk for becoming obese due
                                           debated, most sources agree that a goal of 1%                                 to the changes in their hormonal balance that
                                           weight loss per week or 3% to 4% per month                                    affect appetite, energy balance, and fat metab-
                                           is a safe target.8,12,29 If, during periods of moni-                          olism. Because of these changes, food intake
                                           toring, this goal is not being achieved, calories                             must be carefully restricted following gonadec-
                                           must be reduced by 5% to 10% and the effects                                  tomy in all cats, and free-choice feeding of dry
                                           of the new amount monitored.                                                  foods should be strongly discouraged.
                                               To achieve loss of fat mass, the weight-loss                                 In indoor cats, for which exercise is reduced
                                           program must consider the cat’s body condition                                by the nature of their lifestyle, energy restric-
                                           at the start of weight loss, the degree of calorie                            tion also becomes paramount to preventing or
                                           restriction required, the desired rate of weight                              correcting obesity. Energy restriction can be
                                           loss, and the cat’s environment and ability to                                achieved by low-fat, high-fiber diets, but many
                                           increase exercise.29 Box 2 provides a step-by-                                of these diets are not high enough in protein to
                                           step overview of the process. Although this strat-                            preserve muscle and thus result in loss of mus-
                                           egy is relatively straightforward (reduce energy                              cle mass, unhealthy weight loss, and a strong
                                           intake), it requires patience; careful, long-term                             tendency to regain weight. High-protein, low-
                                           monitoring; encouragement and support for the                                 carbohydrate, low-fat diets are ideal for weight
                                           owner; and frequent assessment and readjust-                                  loss in cats because they preserve muscle mass
                                           ment to meet the needs of the cat.                                            while restricting energy sources to induce fat
                                                                                                                         loss. However, portion control is ultimately the
                                                     Conclusion                                                          key to controlling energy intake and is most
    to lEarn
                                                     The key to obesity prevention (or cor-                              easily achieved by feeding canned food with a
                                                     rection) is balancing the energy intake/                            protein content of >45% ME and a carbohydrate
                                                     energy expenditure equation. Because                                content of <10% ME. The key to any success-
    For a more detailed                              obesity is incredibly difficult to reverse                          ful weight-loss program is patience, persistence,
    discussion of how free-choice                    in adult cats and, in many cases, requires                          frequent and careful monitoring and assessment,
    feeding negatively affects
                                                     lifelong management because of changes                              and readjustment of the caloric intake and diet
    cats’ health, please visit
                                                     in energy metabolism and hormone status,                            as needed to achieve fat loss and preserve lean
                                                     prevention is an essential goal. All neu-                           muscle tissue.

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 1. A cat with an ideal weight of ____lb and an                       hormonal imbalances after neutering.                      8. In neutered cats, energy intake recommen-
    actual weight of ____lb would meet the cur-                    b. a sedentary, indoor lifestyle.                               dations on commercial food labels must be
    rently accepted definition of obese.                           c. overfeeding.                                                 decreased by approximately ________ to
    a. 9; 9.9                                                      d. all of the above                                             prevent the development of obesity.
    b. 7; 8.2                                                                                                                      a. 20%
    c. 11; 13.5                                                 5. Successful weight loss in obese cats is                         b. 25%
    d. 14; 16.4                                                    characterized by all of the following except                    c. 30%
                                                                   a. preservation of lean muscle mass by                          d. 35%
 2. Cats digest carbohydrates differently from                        feeding a high-protein diet.
    omnivores because they                                         b. loss of fat mass at a rate of 1% to 2%                    9. Which statement regarding label recom-
    a. have high levels of intestinal amylase.                        per week.                                                    mendations for feeding cats is true?
    b. lack salivary amylase.                                      c. control of caloric intake by meal feeding                    a. They are based on twice the mainte-
    c. have increased function of hepatic                             and portion control.                                            nance energy requirement.
       glucokinase.                                                d. activity restriction.                                        b. They are based on the needs of intact,
    d. have high levels of fructokinase.                                                                                              active cats.
                                                                6. Which condition has not been associated                         c. Pet food manufacturers overestimate
 3. Which feeding approach is most likely to                       with obesity in cats?                                              energy needs to avoid underfeeding
    lead to healthy weight loss?                                   a. hepatic lipidosis                                               cats.
    a. meal feeding of high-carbohydrate dry                       b. hypertrophic cardiomyopathy                                  d. They are based on the needs of neu-
       food only                                                   c. diabetes mellitus                                               tered cats.
    b. free-choice feeding of high-carbohydrate                    d. osteoarthritis
       canned food only                                                                                                         10. Weight-loss diets for obese cats
    c. free-choice feeding of high-protein dry                  7. Which clinical method of evaluating                              should contain _______ ME of protein
       food only                                                   body fat mass in cats is most likely to be                       to promote fat loss and prevent loss of
    d. meal feeding of high-protein canned                         affected by technical issues?                                    muscle mass.
       food only                                                   a. BCS                                                           a. >30%
                                                                   b. morphometric measurement                                      b. >35%
 4. Risk factors for obesity in cats include                       c. BIA                                                           c. >40%
    a. appetite and energy changes caused by                       d. BMI                                                           d. >45%

                                                                  CompendiumVet.com | June 2009 | Compendium: Continuing Education for Veterinarians®                               293

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