The study, published in Frontiers in Animal Science, was led by Andrew Knight of Murdoch University, together with Alexander Bauer and Jenny L. Mace. The team conducted a cross-sectional online survey of companion animal carers, open from May to December 2020, which gathered information on the health of one resident cat per household that had lived there for at least a year. From a larger pool of 4,057 dog and cat carers, 1,397 cat carers met the inclusion criteria, and 1,305 cats were ultimately analysed across the two diet groups of interest: 1,178 cats, or 90.3 percent, fed conventional meat-based diets, and 127 cats, or 9.7 percent, fed vegan diets for at least one year. Carers reported the assessments of their primary veterinarians concerning the cats’ health over the previous twelve months.

The researchers focused on six body weight-related disorders: overweight, underweight, osteoarthritis or arthritis, intervertebral disc disease, other mobility disorders, and other musculoskeletal problems. According to the carer-reported veterinary assessments, only 3.1 percent of vegan-fed cats were classified as overweight, compared with 4.1 percent of meat-fed cats. In unadjusted statistical analyses, cats fed vegan diets had odds of being overweight that were 24 percent lower than their meat-fed counterparts. When the researchers adjusted for ten potential confounding variables, including age, sex, neuter status, activity level and a range of feeding practices, the difference widened to 34 percent lower odds of overweight in the vegan group.

Here is the crucial caveat: neither figure reached statistical significance. The confidence intervals were wide, spanning from a 73 percent reduction to a 116 percent increase in the unadjusted overweight analysis, reflecting the relatively small number of observed cases. Only four vegan-fed cats were classified as overweight at all. The authors interpreted the raw 24 percent effect as a “tendency” and the adjusted 34 percent effect as a “strong tendency,” using heuristic categories they established in earlier work on general health outcomes from the same survey. Following the American Statistical Association’s guidance on p-values, they emphasised effect strength over binary significance thresholds, but they are explicit that the findings should be treated as hypothesis-generating rather than confirmatory.

The pattern extended to underweight as well. Cats fed vegan diets showed 66 percent lower odds of being underweight in the unadjusted models, a difference the authors labelled a strong tendency, though again it was not statistically significant. More striking still were the secondary outcomes: not a single vegan-fed cat in the sample was reported to suffer from osteoarthritis or arthritis, intervertebral disc disease, other mobility disorders, or other musculoskeletal problems. Among the meat-fed group, 15 cats had arthritis impairing mobility, one had intervertebral disc disease, eight had other mobility problems and 14 had other musculoskeletal problems. Because zero cases occurred in the vegan group, the researchers could not run regression models for these outcomes at all, and the low prevalence likely reflects the small size of the vegan subgroup rather than any proven protective effect.

The statistical machinery behind the study was deliberately cautious. The analysis proceeded in three steps: a descriptive stage, an exploratory stage estimating the diet effect with ten separate one-variable regression models, and a final fully adjusted model restricted to outcomes with at least 50 cases across both diet groups, a criterion met only by overweight. That final model produced an area under the curve of 0.78 on a held-out test set, indicating acceptable fit. Two sensitivity analyses bolstered the findings: propensity score matching on age, which matters because vegan-fed cats averaged 6.2 years old versus 8.2 years for meat-fed cats, yielded broadly similar reductions of 21 percent in overweight and 50 percent in underweight odds. And when 64 raw-meat-fed cats were folded into the meat-based comparison group, the results barely moved, with the adjusted overweight effect shifting by just one percentage point.

Why might plant-based diets be associated with leaner cats? The authors cannot answer definitively, since they collected no compositional data, but they outline plausible mechanisms. Nutritional guidelines for weight management in cats favour lower calories, lower fat, higher fibre and higher L-carnitine content. Plant-derived ingredients often contain more fibre and potentially fewer calories or less fat than animal sources. More intriguingly, conventional cat foods are not required to guarantee L-carnitine, a vitamin-like amino acid derivative critical for energy metabolism and the retention of lean body tissue, because manufacturers assume meat supplies adequate quantities. Some nutritionally sound vegan cat foods, by contrast, are explicitly supplemented with L-carnitine, potentially offering cats greater protection against weight gain. There is also a paradox worth noting: vegan-fed cats in this sample were actually more often fed dry food and fed ad libitum, both factors previously associated with increased overweight risk, yet they still showed lower odds of excess weight.

The study also surfaced a striking discrepancy in how weight was judged. Veterinarians reportedly considered 94 percent of meat-fed cats and 96 percent of vegan-fed cats to be at ideal weight, while carers’ own opinions put those figures at 70 percent and 76 percent respectively. Usually the reverse is true, with owners less likely than vets to recognise overweight. The authors suggest several explanations: carer concern may capture perceived adiposity rather than clinically communicated problems; body condition scoring is under-recorded in practice, with a UK study of 129,076 cat visits finding weight recorded in only 10 percent of visits; and surveys may attract more health-conscious carers. The very low 4 percent veterinary-reported overweight prevalence in this sample contrasts sharply with estimates of 30 to 60 percent from veterinary-assessed studies, which may mean the study underestimated overweight overall, a limitation the authors acknowledge candidly.

That said, the limitations extend further. All outcomes relied on carer reports, introducing potential recall and reporting bias, and carer-reported assessments are not equivalent to standardised veterinary body condition scoring. Social desirability bias among vegan-feeding carers, possible confounding by unmeasured health-protective behaviours, and survivorship bias, in which cats harmed by vegan diets are switched back to meat and vanish from the vegan group, cannot be excluded. The analysis also excluded endocrine, urinary, cardiac and dermatological comorbidities of obesity. The fully adjusted model, with only four overweight events in the vegan group, fell short of the traditional ten-events-per-parameter rule of thumb for logistic regression.

What the study does deliver is a consistent direction of effect across every model the authors ran, a robustness to alternative analytical choices, and a clear roadmap for future work. Larger samples, prospective designs, direct extraction of veterinary-recorded body weights and standardised body condition scores, and measurement of actual diet composition and energy intake would all help resolve whether the leaner-cats pattern is real. For now, the message is nuanced: among these 1,305 cats, vegan-fed animals fared no worse on body weight and related disorders than meat-fed ones, and descriptively better, but nobody should yet conclude that vegan diets slim down cats. This is exploratory science, published transparently with its uncertainty on display, precisely so that the next generation of studies can test the hypothesis properly.

Subject of Research: The association between vegan versus meat-based diets and body weight-related disorders in domestic cats

Article Title: Impacts of a vegan diet on body weight and related health disorders in 1,305 cats: an exploratory cross-sectional survey

Article References: Knight, A., Bauer, A., & Mace, J. L. (2026). Impacts of a vegan diet on body weight and related health disorders in 1,305 cats: an exploratory cross-sectional survey. Frontiers in Animal Science, 7, Article 1939965. https://doi.org/10.3389/fanim.2026.1939965

Image Credits: AI Generated

DOI: 10.3389/fanim.2026.1939965

Keywords: cats, vegan cat food, feline obesity, overweight, body condition score, pet nutrition, veterinary epidemiology, cross-sectional survey, logistic regression, obligate carnivores, L-carnitine, pet health