Effects of neutering on food intake, body weight and body composition in growing female kittens

A Prospective Study of Growth Rate, Disease Incidence, and Mortality in Kittens Less than 9 Weeks of Age in Shelter and Foster Care

A prospective study was designed to (a) investigate the rate of daily weight gain among kittens less than 9 weeks old presented to an animal shelter, (b) identify factors (e.g., sex, clinical signs of disease, diet, and medical treatment) that affect daily weight gain, and (c) investigate the mortality of study kittens. The study of 203 kittens was conducted at a managed admission, no-kill animal shelter in upstate New York, USA, from April 2014 through October 2014. Body weight was measured daily from day of intake to adoption or 12 weeks of age. Fecal score, clinical signs of disease, food type, and medical treatments were recorded daily. Lethargy and being female were significantly associated with lower daily weight gain. Despite the challenges of shelter and foster care, the average daily weight gain for study kitten was higher than that reported in other settings such as catteries and laboratories. Five study kittens (2.5%) died or were euthanized. Daily monitoring systems provide opportunities for interventions, increased live outcomes, and improved welfare for kittens in shelter and foster care.

Comparison of growth in neutered Domestic Shorthair kittens with growth in sexually-intact cats

The first aim of these studies was to compare growth patterns of healthy kittens neutered during growth with growth standards created for sexually-intact kittens. A second aim was to clarify the impact of neutering in kittens on body composition and body shape. Study 1 was a retrospective observational study comparing median growth trajectories of healthy, client-owned domestic shorthair (DSH) kittens in optimal body condition and neutered at different ages, with previously-created growth standards from a similar, sexually-intact, population. The neuter groups contained between 3.0k and 9.3k cats. For all neuter groups in both sexes, the median growth trajectory inclined upwards after the procedure, with this being more marked in female than in male kittens. This upwards inclination was less marked for kittens neutered later during growth in both sexes, with the effect being least in kittens neutered after 28-29 weeks. Study 2 was an analysis of new body composition and zoometric data from a previously-published randomised study, comparing growth-related measures between 11 pairs of sexually-intact and neutered (at 19 weeks age) female DSH cats in a research population. Before neutering, the growth pattern in neutered kittens and sexually-intact kittens was similar, but neutered kittens were heavier by 52 weeks (mean difference in fold change vs. 10 weeks 1.34, 95-CI: 1.07-1.72), had a greater fat mass (mean difference in fold change vs. 10 weeks 1.91, 95-CI 1.09-3.21) and greater lean mass (mean difference in fold change vs. 10 weeks 1.23, 95-CI: 1.03-1.48). Abdominal girth (mean difference in fold change vs. 10 weeks 1.20, 95-CI: 1.04-1.39) and rib cage length (mean difference in fold change vs. 10 weeks 1.18, 95-CI: 1.02-1.36) were also greater, but there were no differences in other zoometric measurements. Veterinarians should consider the potential impact that neutering has on gain of adipose tissue, especially early neutering in female kittens. Bodyweight should be monitored closely during growth and especially after neutering to prevent inappropriate weight gain.

Environmental risk factors in puppies and kittens for developing chronic disorders in adulthood: A call for research on developmental programming

Many dogs and cats are affected by chronic diseases that significantly impact their health and welfare and relationships with humans. Some of these diseases can be challenging to treat, and a better understanding of early-life risk factors for diseases occurring in adulthood is key to improving preventive veterinary care and husbandry practices. This article reviews early-life risk factors for obesity and chronic enteropathy, and for chronic behavioral problems, which can also be intractable with life-changing consequences. Aspects of early life in puppies and kittens that can impact the risk of adult disorders include maternal nutrition, establishment of the gut microbiome, maternal behavior, weaning, nutrition during growth, growth rate, socialization with conspecifics and humans, rehoming and neutering. Despite evidence in some species that the disorders reviewed here reflect the developmental origins of health and disease (DOHaD), developmental programming has rarely been studied in dogs and cats. Priorities and strategies to increase knowledge of early-life risk factors and DOHaD in dogs and cats are discussed. Critical windows of development are proposed: preconception, gestation, the suckling period, early growth pre-neutering or pre-puberty, and growth post-neutering or post-puberty to adult size, the durations of which depend upon species and breed. Challenges to DOHaD research in these species include a large number of breeds with wide genetic and phenotypic variability, and the existence of many mixed-breed individuals. Moreover, difficulties in conducting prospective lifelong cohort studies are exacerbated by discontinuity in pet husbandry between breeders and subsequent owners, and by the dispersed nature of pet ownership.

Growth standard charts for monitoring bodyweight in intact domestic shorthair kittens from the USA

The optimal growth of domesticated cats has not yet been well defined. This study first aimed to create evidence-based growth standards for healthy pet domestic shorthair (DSH) kittens, and then compare the pattern of growth curves depicted by the standards with growth patterns in other healthy DSH kittens and those with abnormal body condition. Data were derived from the clinical records of the BANFIELD® Pet Hospital (BANFIELD) network in the USA and from a research population in the UK (Waltham Petcare Science Institute, UK). A 'modelling' dataset was first created from the BANFIELD records, comprising bodyweight data from immature client-owned DSH cats that had remained healthy and in ideal body condition within the first 2.5y of life. This was used to construct growth centile curves for male and female kittens, covering the age range 8 to 78 weeks, using Generalised Additive Models for Location, Shape and Scale. Growth patterns depicted by the centile curves were compared with the growth patterns of healthy DSH kittens from both research colonies and kittens attending BANFIELD that were classified as overweight or underweight. Overall, there was a broad agreement to the growth standards with approximately half of the research population (206/507, 49%) staying within 2 centile lines of their starting centile, and upward and downward movements outside this range being roughly equally distributed. Compared with the growth standards, the 122 overweight BANFIELD kittens were heavier on average at the start of monitoring and subsequently grew more quickly with 63 (52%) crossing at least 2 standard centile lines upwards. Only 4 underweight DSH kittens were available in the BANFIELD database; compared with the standards, there was a marked initial dip in growth followed by subsequent catch-up growth and 2/4 kittens crossed 2 or more centile lines downwards at some point. Evidence-based growth standards are developed here for male and female sexually-intact DSH kittens. Crossing centiles in an upwards and downwards direction is associated with cats becoming overweight or underweight by early adulthood, respectively. Further work is required to determine whether the clinical use of these growth standards will improve the health and wellbeing of pet cats.

Prevalence, risk factors, and disease associations of overweight and obesity in cats that visited the Veterinary Medical Teaching Hospital at the University of California, Davis from January 2006 to December 2015

Overweight and obesity are commonly diagnosed in domestic cats, and undermine cats' quality of life directly or indirectly via various disease processes known to be associated with overweight and obesity. Epidemiological studies have reported varied overall prevalence among different feline populations, and commonly identified risk factors such as neutering. However, disease associations were not consistently reported. The status of feline overweight and obesity in a referral veterinary teaching hospital in the United States remains undefined as well. The present study used descriptive statistics and logistic regression models to analyze feline medical records obtained at the Veterinary Medical Teaching Hospital at the University of California, Davis from January 2006 to December 2015 and to characterize the prevalence of overweight and obesity, risk factors, and disease associations. In 9,062 feline records analyzed, the overall prevalence of overweight (17.2%; n = 1,560) and obesity (23.8%; n = 2,160) was 41.0%. Neutered, male, and crossbred cats that were in age groups between 3.0 and 14.9 years old and presented with disease processes in orthopedic, dentistry, and urinary categories were positively associated with overweight and obesity. Overweight and obesity are prevalent problems, which can benefit from continual veterinary education emphasizing its importance. Structured disease surveillance plans monitoring these associated factors also help guide further research and ideally can contribute to development of better prevention strategies for overweight and obesity.

Domestic cats (Felis catus) prefer freely available food over food that requires effort

Contrafreeloading is the willingness of animals to work for food when equivalent food is freely available. This behavior is observed in laboratory, domesticated, and captive animals. However, previous research found that six laboratory cats failed to contrafreeload. We hypothesized that cats would contrafreeload in the home environment when given a choice between a food puzzle and a tray of similar size and shape. We also hypothesized that more active cats would be more likely to contrafreeload. We assessed the behavior of 17 neutered, indoor domestic cats (Felis catus) when presented with both a food puzzle and a tray across ten 30-min trials. Each cat wore an activity tracker, and all sessions were video recorded. Cats ate more food from the free feed tray than the puzzle (t (16) = 6.77, p < 0.001). Cats made more first choices to approach and eat from the tray. There was no relationship between activity and contrafreeloading, and there was no effect of sex, age, or previous food puzzle experience on contrafreeloading. Our results suggest that cats do not show strong tendencies to contrafreeload in the home environment, although some cats (N = 4) ate most food offered in the puzzle or showed weak contrafreeloading tendencies (N = 5). Eight cats did not contrafreeload. Cats who consumed more food from the puzzle, consumed more food in general, suggesting a relationship between hunger and effort. Further research is required to understand why domestic cats, unlike other tested species, do not show a strong preference to work for food.

Energy Requirements for Growth in the Norfolk Terrier

An appropriate energy intake for healthy growth can reduce the risk of obesity and co-morbidities, such as orthopaedic diseases. The 2006 National Research Council (NRC) universal equation calculates the energy requirement of growing dogs based on predicted adult body weight, but evidence suggests a revision may be required. This study investigates the energy requirements of seventeen Norfolk terrier puppies over their first year (10 to 52 weeks). Puppies were individually fed complete and balanced diets in amounts to maintain an optimal body condition score (BCS), recording intake daily and body weight and BCS weekly. To monitor health a veterinary examination, haematology and plasma biochemistry and serum measures of bone turnover were undertaken every 12 weeks. Skeletal development was assessed using dual-energy X-ray absorptiometry (26 and 52 weeks). Puppies were clinically healthy with normal skeletal development and healthy growth throughout. The energy intake to achieve this was significantly lower than that predicted by the NRC (2006) equation at all time points, with largest mean difference of 285 kJ/kg^0.75 per day at 10 weeks. If fed according to the NRC 2006 equation, dogs would have been in positive energy balance, possibly leading to obesity. These data support a revision to the NRC (2006) equation.

Growth Curve and Energy Intake in Male and Female Cats

The aim of this study were (1) to characterize the growth curve in male and female cats, (2) to associate the growth and metabolizable energy intake (MEI) as an indirect measurement of the energy requirements, and (3) to determine the short-term effects of neutering on energy intake to maintain the bodyweight in young adult cats. Eighteen 5-months-old mixed breed cats were used in this study (males, n = 7 and BW = 2.2 ± 0.21 kg; females, n = 11 and BW = 2.0 ± 0.16 kg). The cats were fed to supply their metabolizable energy requirement for growth, adjusting the amounts to maintain an ideal body condition score. The animals were weighed every 15 days for 10 months (from 5 to 15 months old). At 12 months old, the cats were gonadectomized and the MEI was recorded for 3 months, up to 15 months old. Second-order, Gaussian, and spherical models were fitted to growth data. Male cats had higher energy intake for growth (MEI = 176.27^-0.037t, R² = 0.79) than females (MEI = 166.86^-0.044t, R² = 0.62), where t is the age in months. Male cats also reached mature weight later than female cats (16 and 13 months old, respectively). Neutering reduced the energy requirements of male (intact - 116.43 kcal/kg^0.67; gonadectomized - 98.65 kcal/kg^0.67; P < .01) and female cats (intact - 98.65 kcal/kg^0.67; gonadectomized - 76.16 kcal/kg^0.67; P < .01) on average 17.6%. This study suggests that in cats, males and females present different energy requirements since the early growth phases and, this difference remains after neutering in young adults. Female cats reach adult weight earlier than males.

Owner and Cat-Related Risk Factors for Feline Overweight or Obesity

Feline obesity is a highly prevalent disease that poses an urgent and serious challenge. Attempted treatment by weight reduction is often unsuccessful; a new preventative approach that focuses on the role of the owner may be helpful. This study used data collected from an international survey of cat owners designed to assess owner personality and self-control, owner-pet attachment, feeding practices, and the cat's body condition. Owner-reported body condition scores (BCS) of cats were assessed using images adapted from a 5-point BCS system and categorized as a binary dependent variable: overweight/obese (BCS 4-5) and not overweight (BCS 1-3). Owner-reported BCS scores using a verbal BCS scale were also used as a binary dependent variable. Of the 6,835 respondents, 30.5% described their cat as overweight/obese using the visual BCS scale, and 32.5% using the verbal scale. Multivariable logistic regression models were built using stepwise-backward selection. A total of 8 variables were significant using the visual score as the dependent variable, while 11 variables were significant using the verbal score as the dependent variable (p < 0.05). Low owner conscientiousness was associated with an increased risk of feline overweight/obesity (OR = 1.23, 95% CI 1.10-1.38), whereas preference for delayed reward was associated with a decreased risk (OR = 0.84, 95% CI 0.75-0.96). Contrary to expectation, indulgent (OR = 0.76, 95% CI 0.53-0.91) and inconsistent (OR = 0.86, 95% CI 0.76-0.93) feeding practices appeared protective. Other significant variables (p < 0.05) included cat-related factors (age, gender, housing, source) and management-related factors (dry diet, supermarket dry diet, raw diet, stealing, hunting, and measuring food with a scoop). A third multivariable analysis was performed, using results from cats classified as overweight/obese using both scoring methods, compared with cats classified as a healthy weight using both scoring methods. A total of 10 variables were found to be significant (p < 0.05). There was significant overlap of results from all three analyses. The results of this study indicate that feline obesity is a complex problem, with many contributing risk factors. It is essential to recognize the importance of owner characteristics, and that the prevention of obesity in cats may require the development of a range of interventional strategies.

Owner and Cat-Related Risk Factors for Feline Overweight or Obesity

Feline obesity is a highly prevalent disease that poses an urgent and serious challenge. Attempted treatment by weight reduction is often unsuccessful; a new preventative approach that focuses on the role of the owner may be helpful. This study used data collected from an international survey of cat owners designed to assess owner personality and self-control, owner-pet attachment, feeding practices, and the cat's body condition. Owner-reported body condition scores (BCS) of cats were assessed using images adapted from a 5-point BCS system and categorized as a binary dependent variable: overweight/obese (BCS 4-5) and not overweight (BCS 1-3). Owner-reported BCS scores using a verbal BCS scale were also used as a binary dependent variable. Of the 6,835 respondents, 30.5% described their cat as overweight/obese using the visual BCS scale, and 32.5% using the verbal scale. Multivariable logistic regression models were built using stepwise-backward selection. A total of 8 variables were significant using the visual score as the dependent variable, while 11 variables were significant using the verbal score as the dependent variable (p < 0.05). Low owner conscientiousness was associated with an increased risk of feline overweight/obesity (OR = 1.23, 95% CI 1.10-1.38), whereas preference for delayed reward was associated with a decreased risk (OR = 0.84, 95% CI 0.75-0.96). Contrary to expectation, indulgent (OR = 0.76, 95% CI 0.53-0.91) and inconsistent (OR = 0.86, 95% CI 0.76-0.93) feeding practices appeared protective. Other significant variables (p < 0.05) included cat-related factors (age, gender, housing, source) and management-related factors (dry diet, supermarket dry diet, raw diet, stealing, hunting, and measuring food with a scoop). A third multivariable analysis was performed, using results from cats classified as overweight/obese using both scoring methods, compared with cats classified as a healthy weight using both scoring methods. A total of 10 variables were found to be significant (p < 0.05). There was significant overlap of results from all three analyses. The results of this study indicate that feline obesity is a complex problem, with many contributing risk factors. It is essential to recognize the importance of owner characteristics, and that the prevention of obesity in cats may require the development of a range of interventional strategies.

Body composition of lean outdoor intact cats vs lean indoor neutered cats using dual-energy x-ray absorptiometry

OBJECTIVES

The objectives for this study were to compare the body composition of adult indoor neutered domestic cats with outdoor intact cats with an ideal body condition score using dual-energy x-ray absorptiometry, and to report the body composition findings of free-roaming cats, as this has not been previously reported. Most domestic house cats differ from free-roaming cats as they are confined indoors and neutered. Indoor neutered cats have reduced activity and hormonal alterations that may result in lower muscle mass and higher body fat percentages vs outdoor intact cats, despite similar body condition scores.

METHODS

Twenty-one outdoor intact cats (10 male, 11 female) were selected from a trap-neuter-return program and 16 indoor neutered domestic cats (10 male, six female) were client-owned. Inclusion criteria included an estimated age between 1 and 6 years, complete blood count, biochemistry panel, urinalysis, total thyroxine, feline leukemia virus/feline immunodeficiency virus screening and a body condition score of 4-5/9.

RESULTS

Indoor neutered cats had a higher body fat percentage (22.1% [range 17.3-28.2%]) than outdoor intact cats (17.3% [range 10.0-33.6%]; P = 0.002). Indoor neutered male cats had a higher body fat percentage ( P <0.001) than outdoor intact cats. No difference in body fat percentage was observed in female cats ( P = 0.159). Indoor neutered domestic cats had a higher bone mineral density than outdoor intact cats ( P = 0.023).

CONCLUSIONS AND RELEVANCE

The results of this study suggest indoor confinement and neutering increase body fat percentage and bone mineral density in cats with an ideal body condition score.

PANCOSMA COMPARATIVE GUT PHYSIOLOGY SYMPOSIUM: ALL ABOUT APPETITE REGULATION: Effects of diet and gonadal steroids on appetite regulation and food intake of companion animals

The prominent incidence of overweight and obese pet animals not only results in higher morbidity and mortality, but also poses a threat for the quality of life, longevity, and well-being of dogs and cats. To date, strategies to prevent BW gain or to induce weight loss have had modest success in the pet population. In part, due to the complexity and the multifactorial nature of this disease, which involves pet-human interaction, environmental and dietary factors, and an intertwined metabolic process that still is not fully understood. As such, research methods to investigate the role of physiological hormones and dietary management on mechanisms related to the control of feelings of satiety and hunger in pet animals is warranted. Increasing interest exists in exploring gut chemosensing mechanisms, the crosstalk between metabolic-active tissues, and the interface between the gut microbiota and the nervous system (gut-brain axis). The noninvasive nature of research conducted in companion animals focuses on systemic approaches to develop environmental, nutritional, or therapeutic interventions that can be translated from research settings to pet-owned households. Because the majority of the pet population is spayed or neutered, it is important to determine the effect that sex hormones might have on appetite regulation and fasting metabolic rate of these animals. In general, studies have revealed that gonadectomy may establish a new "set point" characterized by increased food intake and BW, accompanied by physiological and behavioral changes. Some studies have also shown associations between gonadectomy and alterations in appetite-related hormones (e.g., ghrelin, leptin, adiponectin, glucagon-like peptide-1). Manipulation of macronutrients in diets of dogs and cats have also been investigated as a mean to improve satiety. Most of the research in this area has focused on high-protein diets, predominantly, for cats, and the use of dietary fiber sources of contrasting fermentability and viscosity profiles. Dietary fibers may affect the production of fermentative end products and gut microbiome, digestive and absorptive processes, appetite-related hormones, and promote "gut fill" and satiety. More recent studies have reported profound effects of dietary manipulation on the phylogeny and functional capacity of gut microbial communities of dogs and cats.

Risk of obesity in the neutered cat

Surgical neutering is one of the most common procedures performed on pets in the USA among other countries. There are known effects of neutering on the physiology and behavior of the cat that predispose to obesity, which is the most significant sequela from a nutritional perspective. Increased food intake is the most likely factor influencing weight gain in the neutered cat. Proactively addressing these changes with nutritional management strategies can help prevent weight gain and associated negative consequences.

The impact of time of neutering on weight gain and energy intake in female kittens

Neutering is a risk factor for obesity in companion animals. In a study to determine the total energy requirements of kittens (15-52 weeks) the impact of neutering and age when neutered on intake and body weight (BW) was investigated. Females (n 14), neutered when 19 (early neuter; EN) or 31 (conventional neuter; CN) weeks old (n 7/group), were individually fed to maintain an ideal body condition score (BCS). EN kittens gained weight gradually whilst CN kittens' BW gain slowed from week 24, weighing less than EN kittens from week 30 with a reduced energy intake (kcal/kg BW^0·67) in weeks 24-32 (P < 0·05). Following neutering, CN cats' BW and energy intake increased rapidly (energy intake CN > EN in weeks 36-40). Although EN required earlier diet restriction, acute hyperphagia and increased rate of BW gain following neutering were not observed. Earlier neutering may aid healthy weight management through growth when regulating intake to maintain an ideal BCS.

Metabolic Profiling Reveals Effects of Age, Sexual Development and Neutering in Plasma of Young Male Cats

Neutering is a significant risk factor for obesity in cats. The mechanisms that promote neuter-associated weight gain are not well understood but following neutering, acute changes in energy expenditure and energy consumption have been observed. Metabolic profiling (GC-MS and UHPLC-MS-MS) was used in a longitudinal study to identify changes associated with age, sexual development and neutering in male cats fed a nutritionally-complete dry diet to maintain an ideal body condition score. At eight time points, between 19 and 52 weeks of age, fasted blood samples were taken from kittens neutered at either 19 weeks of age (Early Neuter (EN), n = 8) or at 31 weeks of age (Conventional Neuter (CN), n = 7). Univariate and multivariate analyses were used to compare plasma metabolites (n = 370) from EN and CN cats. Age was the primary driver of variance in the plasma metabolome, including a developmental change independent of neuter group between 19 and 21 weeks in lysolipids and fatty acid amides. Changes associated with sexual development and its subsequent loss were also observed, with differences at some time points observed between EN and CN cats for 45 metabolites (FDR p<0.05). Pathway Enrichment Analysis also identified significant effects in 20 pathways, dominated by amino acid, sterol and fatty acid metabolism. Most changes were interpretable within the context of male sexual development, and changed following neutering in the CN group. Felinine metabolism in CN cats was the most significantly altered pathway, increasing during sexual development and decreasing acutely following neutering. Felinine is a testosterone-regulated, felid-specific glutathione derivative secreted in urine. Alterations in tryptophan, histidine and tocopherol metabolism observed in peripubertal cats may be to support physiological functions of glutathione following diversion of S-amino acids for urinary felinine secretion.

Scope of the Problem and Perception by Owners and Veterinarians

Obesity is a common disease of modern dogs and cats. Dog and cat owners often do not realize their animal is affected. Some pet owners are skeptical of the diagnosis or rationalize the overweight condition of their pets. Animal-related factors associated with obesity in dogs and cats include breed, neuter status, age, and gender, whereas owner-related factors include diet choice, feeding method, and provision of exercise. Owner characteristics, such as age and income, are also potential risk factors for pet obesity. Identifying such risk factors for both animals and owners may help provide targets for prevention or interventional tools.

Relationship between age at gonadectomy and health problems in kittens adopted from shelters

Prepubertal gonadectomy (PPG) is promoted as a way of managing overpopulation in cats, but concerns about PPG and potential health issues still exist. The objective of the present study was to evaluate short-term and long-term health problems in cats subjected to PPG in comparison to gonadectomy at traditional age (TAG). In a prospective clinical trial, 800 shelter kittens aged between approximately 8 weeks and 12 weeks were recruited before adoption and randomly assigned to either the PPG group (gonadectomy performed immediately) or the TAG group (gonadectomy delayed until six months to eight months of age). Short-term health issues included mortality between when kittens arrived at the clinic and up to seven days after they returned to the shelter, as well as the occurrence of various other health issues arising in the first month following adoption. Kittens were followed-up until 24 months of age specifically for feline lower urinary tract disease, urethral obstruction (male cats), lameness, fractures and hypersensitivity disorders with dermatological presentation. In the short term, there were no significant differences between health problems in PPG and TAG kittens. Similarly, no significant differences were observed between treatment groups in terms of the type or number of health issues in the long term. In conclusion, there are no health-related contraindications to advocating PPG strategies in shelter cats. Ideally, PPG should be performed at the shelter facility itself as long as excellent infectious disease control and postoperative clinical observation before adoption are guaranteed.

A moderate fat, low-energy dry expanded diet reduces gain in body condition score when fed as part of a post neutering weight-control regimen in growing pet cats

Neutering of cats has been associated with significant weight gain in the weeks following surgery. The present study aimed to evaluate the effectiveness of a moderate fat, low-energy dry expanded diet in reducing weight gain in growing pet cats when fed as part of a weight-control regimen over the 6 months post-neutering. Cats in participating primary care veterinary hospitals were enrolled at neutering and assigned to receive one of the two dietary treatments based on the hospital of origin. Owners of cats in the treatment group were instructed to feed the trial diet at maintenance (324·7 kJ/kg BW^0·711 per d). Instructions for the control group were to feed the cat's regular diet according to the manufacturer's recommendations. Body weight and condition were evaluated by veterinarians at enrolment, 2-weeks, and 1–4 and 6 months after surgery. Body condition score (five-point scale) was compared between enrolment and each subsequent visit, controlling for enrolment age and sex. Percentage change in body weight was evaluated via multivariate mixed modelling to account for repeated measures. A total of 187 cats (eighty-seven females and 100 males) with a mean age of 5·2 (sd 0·8) months and mean weight of 2·8 (sd 0·6) kg from fifty-one hospitals completed the trial. The odds of being scored as overweight were 4·1 times as great for cats in the control v. treatment groups (95 % CI 2·1, 8·2). Percentage change in body weight differed significantly with enrolment age (P = 0·007) and approached significance between diet groups (P = 0·08). Cats fed the trial diet had a significantly reduced incidence of overweight in the 6 months following neutering.