Introduction
The prevalence of overweight condition in US cats is as high as 60%.1 Overweight condition in cats is associated with comorbidities such as insulin resistance, hepatic lipidosis, and urinary tract disease, which compromise QOL.2–4 Caring for overweight cats is expensive; more money is spent on diagnostic procedures (36% more than for nonoverweight cats) and overall care (an estimated additional $1,178/y).5 Thus, weight management of overweight cats may improve QOL and may help resolve or limit the financial burden.
Weight management of overweight cats is multifactorial and includes patient assessment (eg, body weight, BCS), assessment of the current diet, effective client education, client motivation, and a detailed weight loss and monitoring plan.6–9 A detailed diet plan should include a specified diet (ie, food, treats, and other) and instructions on how much and how often to feed. A weight loss diet should facilitate calorie restriction while meeting essential nutrient requirements. Furthermore, a weight loss diet should be low in calories to maximize food provision, which may aid in decreasing negative behaviors (eg, food seeking).10 Commercial veterinary prescription weight loss diets are generally low calorie, high in protein and essential micronutrients, low-fat, and fiber enhanced.11 Specific and clear guidelines regarding how much to feed per day should be provided to the client. Dividing daily food into multiple small meals may help to curb disruptive food-seeking behavior.6 Specific guidelines for treats, including what treats and how many per day, should also be provided.
Cat owners may have concerns about implementing a weight loss plan (eg, concerns with food change and hunger).12 Improving client perception of weight loss may enhance client motivation and compliance, improve the success of weight management plans for overweight cats, and help to reduce the prevalence of overweight condition in cats. Client perception of their dog’s QOL during a prescribed weight loss plan has been evaluated, and QOL improved with weight loss.13 Client perception of their cat’s QOL has been assessed in the context of cancer, osteoarthritis, and cardiac disease management but not in the context of weight management of overweight cats.13–15 Disruptive food-seeking behavior may negatively influence owner-perceived QOL of cats, lead to cheating, and sabotage the prescribed weight loss plan.
Food-dispensing toys have been recommended as an environmental enrichment tool and allow for cats to express their natural predatory nature.16 Food-dispensing toys may slow food consumption, prolong feeding time, increase activity, and decrease time between meals. Therefore, food toys may help curb disruptive food-seeking behavior in cats and improve owner-perceived QOL.
The aim of the study presented here was to determine the effect of a ball-type food toy on owner-perceived QOL of overweight cats during a prescribed weight loss plan. We hypothesized that overweight cats fed by use of a food toy would have a higher QOL.
Materials and Methods
Study cats
The study protocol was approved by the Virginia Tech Institutional Animal Care and Use Committee (No. 16-068) and the Virginia Tech Institutional Review Board (No. 16391). The study was conducted at the Virginia-Maryland College of Veterinary Medicine in Blacksburg, Va. Study participants were recruited from April 2017 to August 2018 for this randomized, double-blind clinical trial by way of oral announcements by the college clinical trials coordinator at local continuing education events, radio advertisement, and the college website. Cats were referred by their veterinarian and included in the study if they had a BCSa ≥ 7 on a 9-point scale and were 1 to 10 years of age, housed indoors with no unattended outdoor access, deemed healthy for weight loss, consuming a primarily dry kibble diet (80% of their diet), and either residing in a single pet household or able to be fed separate from other pets. Regarding health status, referring veterinarians confirmed that cats were free of systemic disease that would render a standard weight loss plan contraindicated (eg, renal disease or cardiac disease) by physical examination, routine laboratory testing, and history; cats were not on medication other than parasite preventatives. Furthermore, owners of enrolled cats needed to be willing to return for monthly recheck examinations and willing to complete the initial and monthly QOL questionnaires. Furthermore, cats were excluded if they were unwilling to consume the commercial veterinary therapeutic weight loss study kibble or if they were too fractious for monthly recheck examinations.
Study protocol
Enrolled cats were weighed, assigned a 9-point BCSa and MCS,b and assigned a random study number by use of a random number generator.c Study numbers coincided with study kits that were prepared by a nonblinded undergraduate research assistant. The kits contained a client consent form, initial questionnaire, monthly questionnaire, commercial dry feline veterinary therapeutic weight loss dietd (single diet for all participants), feeding instructions, measuring cup, and ball-type food toye or food bowl. The initial ME goal for weight loss was calculated as 80% resting energy requirements (70 × body weight [kg] 0.75) for ideal body weight.6 Fifty-five cats were enrolled and randomly assigned to 1 of 2 groups: food toy (n = 26) or food bowl (n = 29) group. The initial and monthly questionnaires were adapted from a previous study.14 For the initial questionnaire, owners ranked the importance of 6 activities in assessing their cat’s QOL from 1 being the most important to 6 being the least important, as follows: eating and drinking, engaging in social activities with humans and pets, resting and observing, grooming and scratching, playing and hunting, and moving from one point to another.14 For the monthly questionnaire completed at the first and subsequent recheck examinations, owners ranked their cat’s ability to perform each of the 6 activities on a scale from 0 (impossible) to 6 (normal). The overall QOL was calculated as previously described by Benito et al.14 The ranking provided for owner-perceived importance of each QOL activity was multiplied by the ability score at each visit. The overall QOL score was the sum of the scores obtained at each visit.
Owners were instructed to transition their cat to the study dietd over a 4- to 8-day period. Cats in the bowl group were instructed to use a 2-bowl technique: one bowl with the cat’s current food and the other with the study diet. The proportion of the current food offered was to gradually decrease in one bowl and the proportion of the recommended diet gradually increased in the other. Cats in the food toy group were instructed to transition the cat to the study diet first and then introduce the food toy. A nonblinded investigator (MLS) reviewed the questionnaires and diet plan, including introducing the food and food toy, with owners and answered their questions throughout the study. The primary investigator (LED) was blinded to cat treatment (food toy vs food bowl).
Owners returned with their cats for monthly recheck examinations to determine body weight, BCS, and MCS; weight loss plan adjustments were made as needed. Monthly recheck examinations were conducted. The weight loss plan was adjusted monthly as needed to achieve a mean weight loss rate of 0.5% to 2%/wk.6 If any cat’s weight loss did not achieve a loss of 0.5%/wk, diet compliance was assessed, and if compliant (feeding 100% of the recommended amount), the weight loss diet was reduced to offer 80% to 90% of prior ME recommendation. Similarly, if any cat’s weight loss rate exceeded 2%/wk, diet compliance was assessed, and if compliant, the weight loss diet was increased to offer 110% to 120% of prior ME recommendation. If cat owners were not compliant, options for maximizing compliance were discussed.
The study for each cat was considered complete once the cat lost ≥ 2 BCS points or reached an ideal BCS of 5/9. Cat owners were debriefed at the end of the study to disclose the purpose of the study (ie, food toy vs food bowl). Owners of cats in the food bowl group were provided with a food toy at the completion of the study.
Statistical analysis
Study outcomes included BCS, MCS, percent body weight loss per week, and owner-perceived QOL. Normal probability plots showed that QOL scores and BCS were skewed, whereas percent body weight loss and percent body weight loss per week followed a normal distribution. Accordingly, skewed data were summarized as median (range) values and normally distributed data were summarized as mean ± SD values.
At baseline, the groups were compared by use of the Fisher exact test (sex and MCS), 2-sample t test (age and body weight), and Wilcoxon rank sum test (BCS). Effects of treatment groups and visit (time during the study) and the interaction between group and visit on QOL (primary outcome) were assessed by use of linear generalized estimating equations. The interaction between group and visit was further analyzed to compare groups within each visit and to compare visits within each group, followed by the Tukey procedure for multiple comparisons. Repeated measures of cats were modeled by use of the compound symmetry correlation matrix. Effects of treatment groups and visit (time during the study) on percent body weight loss per week were assessed by use of a mixed-model repeated-measures ANOVA. The linear models specified treatment group, visit, and interaction between group and visit as fixed effects with Kenward-Roger approximation as the denominator degrees of freedom. G-side variations in data were modeled by means of specifying cat identification within group as a random effect, whereas R-side variations in data were modeled by means of specifying a first order autoregressive covariance matrix. The interaction between group and visit was further analyzed to compare groups at each visit and to compare visits within each group followed by the Tukey procedure for multiple comparisons. The QOL scores (total and for each component separately) for all cats at the start of the study were compared with their last visit by use of the Friedman χ2 test. The QOL scores were also compared between cats that completed the study and cats that did not complete the study, and between cats that achieved a BCS of 5/9 versus cats that lost 2 BCS scores by use of the generalized estimating equations. Change in BCS between first and last visits was compared between groups by use of the Wilcoxon rank sum test, whereas the corresponding change in MCS was compared between the groups by use of the Fisher exact test.
Significance was set at a value of P < 0.05. All analyses were performed by use of statistical software.f
Results
Of the 55 adult client-owned cats enrolled, 11 enrollees were removed from the study for various reasons, including failure to consume the study diet (n = 1), constipation (1), cat stress or behavioral issues (1), inability of the client to return monthly (3), hairballs (1), lost to follow-up (1), hunger (1), lack of improvement (1), and client-suspected adverse food reaction (1). Forty-four cats were included in the final analysis. There was no difference in age, sex, body weight, BCS, or MCS between the food toy and food bowl groups at baseline (Table 1).
Characteristics of 44 cats at baseline during a weight loss plan that were assigned to receive food in a food bowl or a food toy.
| Variable | Unit of measure | Food bowl | Food toy | P value |
|---|---|---|---|---|
| Sex | — | — | — | 0.367 |
| Sexually intact females | Cats (No.) | 0 | 1 | — |
| Spayed females | Cats (No.) | 12 | 9 | — |
| Castrated males | Cats (No.) | 9 | 13 | — |
| Age (y) | Mean ± SD | 5.6 ± 2.5 | 5.1 ± 2.9 | 0.502 |
| Body weight (kg) | Mean ± SD | 7.9 ± 1.3 | 7.8 ± 1.9 | 0.771 |
| BCS | Median (range) | 8 (7–9) | 8 (7–9) | 0.422 |
| MCS* | — | — | — | 0.663 |
| Normal muscle mass | Cats (No.) | 18 | 17 | — |
| Mild muscle loss | Cats (No.) | 2 | 4 | — |
For 3 cats, the volume of subcutaneous fat impeded MCS assessment.
Because of the rolling admission (April 2017 to August 2018) and finite end date for the study (November 2018), there was variation in the number of months each cat was enrolled in the study. Few cats in the food toy group (n = 4) continued past 9 visits; therefore, between-group comparisons for percent body weight loss per week and QOL scores were limited to the first 9 visits of each cat’s weight loss program. Fourteen cats achieved a BCS of 5/9 in a mean of 7.8 ± 3.3 months. Twenty-four cats lost 2 BCS points in a mean of 7.5 ± 2.6 months. The groups did not differ significantly in percent body weight loss per week (P = 0.938; mean ± SD % body weight loss per week: 0.6 ± 0.2% in the food bowl group, 0.7 ± 0.3% in the food toy group), change in BCS (P = 0.451; median [range] BCS change: loss of 1.5 [gain of 0.5 to loss of 3.0] in the food bowl group, loss of 1.0 [loss of 0.0 to 3.0] in the food toy group), and change in MCS (P = 0.321; no change in 15 food bowl group cats, change from normal to mild in 3 food bowl group cats, no change in 9 food toy group cats, change from normal to mild in 1 food toy group cat, change from mild to normal in 2 food toy group cats).
Owners ranked eating and drinking as the most important QOL activity and moving from one point to another as the least important QOL activity for the initial survey (Table 2). There was no significant (P = 0.117) difference in owner-perceived QOL between cats provided a food bowl, compared with cats provided a food toy. However, owner-perceived QOL was significantly (P < 0.001) higher at the last recheck examination, compared with that at the initial examination (Table 3). Owner-perceived QOL activities increased significantly for engaging in social activities with humans and pets (P = 0.018), grooming and scratching (P < 0.001), moving from one point to another (P < 0.001), and playing and hunting (P < 0.001). Of the cats that completed the study (n = 30; each lost 2 BCS points or achieved a BCS of 5/9), owner-perceived QOL was not significantly (P = 0.310) influenced by group (ie, food toy vs food bowl). Although owner-perceived QOL increased for all cats, owner-perceived QOL did not differ significantly (P = 0.664) for cats that completed the study (n = 30; each cat lost 2 BCS points or achieved a BCS of 5/9) versus those that did not (14; each cat lost < 2 BCS points). Also, owner-perceived QOL did not differ significantly (P = 0.820) between cats that achieved an ideal BCS (n = 14; each reached a BCS of 5/9) versus those that lost 2 BCS points but did not achieve an ideal BCS (16).
Median (range) initial ranking of 6 QOL activities obtained on a survey completed by owners of 44 cats enrolled in a weight loss plan.
| QOL activities | Ranking |
|---|---|
| Eating and drinking | 1 (1–5) |
| Engaging in social activities with humans and pets | 3 (1–6) |
| Resting and observing | 4 (1–6) |
| Grooming and scratching | 4 (1–6) |
| Playing and hunting | 4 (1–6) |
| Moving from one point to another | 5 (1–6) |
1 = The most important QOL activity. 6 = The least important QOL activity.
Median (range) initial visit and final visit QOL scores for 6 QOL activities and the sum of QOL activities of cats enrolled in a weight loss plan.
| Variables | QOL scores | P value* | |
|---|---|---|---|
| Initial visit (n = 44) | Final visit (n = 44) | ||
| Eating and drinking | 6 (3–30) | 6 (5–30) | 0.999 |
| Engaging in social activities with humans and pets | 12 (4–36) | 18 (5–36) | 0.018 |
| Grooming and scratching | 18 (3–36) | 24 (4–36) | < 0.001 |
| Moving from one point to another | 20 (4–36) | 30 (5–36) | < 0.001 |
| Playing and hunting | 16 (4–36) | 24 (6–36) | < 0.001 |
| Resting and observing | 18 (6–36) | 24 (6–36) | 0.180 |
| QOL activity sum | 106 (57–186) | 126 (79–210) | < 0.001 |
Values of P < 0.05 indicate a significant difference in values between initial visit and final visit.
For owners that reported disruptive food-seeking behavior, recommendations were provided to offer their cat 0.25 cups of low-calorie vegetable options (eg, zucchini, green beans, cauliflower, lettuce, or broccoli) to feed to promote satiety in their cats while continuing to limit energy intake. Vegetables were chosen because they would add bulk with minimal impact on daily calories. Four of 44 (9.1%) cats consumed vegetables plain. For cats that did not eat plain vegetables (28/44 [63.6%]), a palatability additiveg was used. Twelve of 44 (27.3%) cats were not fed vegetables.
Discussion
To our knowledge, this is the first study to assess owner-perceived QOL in overweight cats on a prescribed weight loss plan. Ability scores were higher for 5 of the 6 activities at the final visit, compared with the initial visit. Owners ranked eating and drinking as the highest QOL activity and moving from one point to another as the lowest QOL activity on the initial questionnaire. Owners may correlate eating and drinking with QOL because decreased food intake is often associated with diminished health. Owners of overweight cats more often use food rather than play as a method of treating, compared with owners of cats with an ideal BCS.17 Therefore, the “food is love” culture appears to extend to household cats, and offering food items may be perceived as an important activity in the human-animal bond.
Our results indicated that no difference existed in perceived QOL scores between cat owners offering food by use of a food bowl versus a food toy. Even though the weight loss plan, including the food toy, was reviewed with owners at the beginning of the study, food toy compliance was not 100%, which likely affected QOL scores. Owners reported variation in how the food-dispensing toy was introduced, which may have affected the cat’s ability to adapt to the food toy. Some owners found it helpful to initially offer the food toy in a pan or area where the food toy couldn’t travel far. Furthermore, other household pets presented a challenge (eg, inability to keep the food toy from other pets). Guidance regarding food toy introduction could have been better defined18 and may have improved compliance and influenced the QOL.
Total QOL scores increased significantly from baseline for both study groups. The QOL scores for engaging in social activities with humans and pets, grooming and scratching, moving from one point to another, and playing and hunting increased significantly and thus appeared to be the primary drivers for increased QOL. In overweight dogs, QOL improved with weight loss and was characterized by higher mean vitality scores, lower mean emotional disturbance scores, and lower pain scores but no change in anxiety scores.13 Improved QOL has also been demonstrated in overweight humans with ≥ 1 comorbidity undergoing a medical weight management program.19 Furthermore, overweight men and women exhibited improved physical and mental composite measures characterized by improved physical functioning, general health, vitality, and mental health subscales after completing a 6-month clinical weight management program.20 Although QOL increased for all cats, no difference was found in owner-perceived QOL between cats successfully completing the study (lost 2 BCS points or reached an ideal BCS), compared with those that were unsuccessful. This result is in contrast to a previous study in which dogs that successfully completed a weight loss program had higher QOL scores, characterized by higher vitality and lower emotional disturbance scores, compared with dogs that did not complete the weight loss program.13
The QOL findings in the present study may not fully reflect the difference in owner-perceived QOL at baseline, compared with follow-up evaluations. After initial weight loss, overscoring of cats’ QOL at baseline was reported by multiple owners, some of whom normalized their cat’s current QOL. Perhaps characterizing the QOL of an overweight cat is challenging because cats are more likely to hide pain and signs of pain can often be subtle.21,22 The questionnaire used in the present study is a general QOL questionnaire adapted from a previous study14 and is not specific to weight loss in cats. In a weight loss study23 involving overweight human adults, 2 generic and a single weight-related QOL measure were compared. Greater improvement in QOL was obtained with the weight-related measure, compared with the generic measures, after the 1-year weight loss trial. A specific weight loss QOL measure may better capture QOL changes during and after weight loss.
The MCS was assessed to subjectively determine whether cats had normal or suboptimal muscle mass throughout the study. Cats were expected to maintain MCS throughout the study. Most cats had normal MCS at the end of the study; 4 cats (3 in the bowl group and 1 in the food toy group) lost 1 MCS score during the study. Because of the limited number of cats that lost MCS and individual variation (eg, final daily energy requirements varied and overlapped with cats with a final normal MCS), a cause cannot be determined. Furthermore, because of the subjective nature of the MCS assessment, future studies investigating the influence of weight loss on muscle mass should consider including more objective methods like dual-energy x-ray absorptiometry.24
Perceived hunger, especially disruptive food-seeking behavior, can be difficult to manage during a weight loss plan. Disruptive food-seeking behavior such as vocalizing, eating a housemate’s food, and opening cabinets to retrieve client’s food was reported in the present study. Such food-seeking behavior resulted in lack of client compliance (eg, feeding increased amounts of food) or potential withdrawal from the study. This is the first study, to the authors’ knowledge, that has implemented low-calorie vegetables to manage or reduce disruptive food-seeking behavior in cats. Zucchini was a commonly suggested vegetable, followed by broccoli, lettuce, green beans, cauliflower, and spinach, typically offered fresh and raw. Some cats preferred several vegetables, some preferred a single vegetable, and 1 cat preferred plain roasted baby zucchini. Most cats consumed vegetables only when combined with a palatability additive.g The additiveg was selected because of its low calorie content (4 kcal/packet/d) and anecdotal high palatability. We suspect the 32 cats offered vegetables would have been removed from the study because of disruptive food-seeking behavior resulting in failure of the weight loss plan. Therefore, inclusion of vegetables should be considered to help managed disruptive food-seeking behavior in overweight cats on a prescribed weight loss plan.
There were several limitations of the present study that should be addressed in future studies that set out to determine how to best implement a weight loss plan in overweight cats. We did not compare food toys, thus there may be other food toys that would influence owner-perceived QOL of cats. Additionally, pairing a food toy with other forms of environmental enrichment may have an additive impact on owner-perceived QOL. The improvement in QOL over time and weight loss in the present study may have limited the ability to detect a benefit of the food toy on QOL. The QOL questionnaire used in the present study was not specifically designed to detect an influence of weight loss. Therefore, designing and validating a QOL questionnaire specific to prescribed weight loss plans for overweight cats would likely be of value to future studies.
Acknowledgments
Food and funding were provided by Nestlé Purina’s Veterinary Residents’ Research Grants Program. The ball-type food toys were provided by PetSafe/Radio Systems Corporation. The sponsors were not involved in the study design or collection or analysis of data.
The authors declare that there were no conflicts of interest.
We acknowledge Montez Vaught, Nutrition Service Coordinator, for her assistance with client communication, scheduling of appointments, and assistance with record keeping; Mindy Quigley, Clinical Trials Coordinator, for her assistance with recruiting study participants and communication; Dr. Michael Nappier, who assisted in the overall study design; and undergraduate volunteers Alexandra Ives, Natasha Welch, and Annie Nguyen for their assistance with the study.
Footnotes
Nine-point BCS scale from World Small Animal Veterinary Association. Available at: wsava.org/wp-content/uploads/2020/08/Body-Condition-Score-cat-updated-August-2020.pdf. Accessed Mar 30, 2021.
Four MCS descriptors from the World Small Animal Veterinary Association. Available at: wsava.org/wp-content/uploads/2020/01/Muscle-Condition-Score-Chart-for-Cats.pdf. Accessed Mar 30, 2021.
Excel 2016, Microsoft Corp, Redmond, Wash.
Purina Pro Plan Veterinary Diets OM Overweight Management dry cat food, Nestlé Purina PetCare Co, St Louis, Mo.
PetSafe SlimCat, Radio Systems Corp, Knoxville, Tenn.
SAS, version 9.4, SAS Institute Inc, Cary, NC.
Purina Pro Plan Veterinary Diets FortiFlora, Nestlé Purina PetCare Co, St Louis, Mo.
Abbreviations
| BCS | Body condition score |
| MCS | Muscle condition score |
| ME | Metabolizable energy |
| QOL | Quality of life |
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