Changes in body composition during weight loss in obese client-owned cats: loss of lean tissue mass correlates with overall percentage of weight lost Alexander J German BVSc, PhD, CertSAM, DipECVIM-CA, MRCVS 1 * , Shelley Holden 1 , Thomas Bissot DVM 2 , Penelope J Morris BSc, PhD 3 , Vincent BiourgeDVM, PhD, DACVN 2 1 Small Animal Teaching Hospital, Department of Veterinary Clinical Sciences, University of Liverpool, Chester High Road, Neston, Wirral CH64 7TE,UK 2 Royal Canin Research Center, Aimargues, France 3 Waltham Centre for Pet Nutrition, Freeby Lane, Waltham-on-the- Wolds,Melton Mowbray, LE14 4RT,UK Obesity is one of the most common medical diseases in cats, but there remains little information on success of weight loss regimes in obese client-owned cats. No information currently exists on body composition changes during weight loss in clinical cases. Twelve obese client-owned cats undertook a weight loss programme incorporating a high-protein low fat diet. Body composition was quantified by dual-energy X-ray absorptiometry, before and after weight loss. Mean (standard deviation) weight loss was 27 6.8% of starting weight, and mean rate of weight loss was 0.8 0.32% per week. Mean energy allocation during weight loss was 32 7.0 kcal/kg target weight. Mean composition of tissue lost was 86:13:1 (fat:lean:bone mineral). The proportion of lean tissue loss was positively associated with overall percentage of weight loss (simple linear regression, r 2 ¼ 44.2%, P ¼ 0.026). Conventional weight loss programmes produce safe weight loss, but lean tissue loss is an inevitable consequence in cats that lose significant proportions of their starting body weight. Date accepted: 27 February 2008 Ó 2008 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved. O besity is defined as an accumulation of excessive amounts of body fat, and is common in cats with prevalence re- ported to be between 22 and 50% (Sloth 1992, Robertson 1999, Russellet al 2000,Harper et al 2001,Lund et al 2005).Given that overweight cats are predisposed to a variety of associated diseases (Lund etal 2005,German 2006) treat- ment is important. Pharmaceutical interventions are now available forthe treatmentof canine obesity (Wren et al 2007), but conventional obe- sity management,involving dietary energy restriction and increasing activity levels, remains the treatmentof choice for cats.A number of research studies have examined the success of weight loss in cats (Butterwick et al 1994, Butter- wick and Markwell 1996,Nguyen et al 2004, Laflamme and Hannah 2005, Michel et al 2005), but such data may notbe fully representative of weight loss in a practice setting, where the variablesare less controlled than in a colony environment. Ideally, adipose tissue alone is lost during weight loss,whilst lean tissue and bone mineral are preserved. A previous study in cats demon- strated thatlean tissue loss is directly propor- tional both to the degree of caloric energy restriction and to the rate of weight loss (Butter- wick and Markwell 1996). This is similar to find- ings in humans (Forbes 1987, Prentice et al 1991) whilst a recent study in dogs has demonstrated that lean tissue loss is proportional to the overall percentage ofweightlost (German etal 2007). Further,work in both dogs and cats has shown dietary composition (eg,high-protein diet)to be important in the relative amounts of the vari- ous body tissues which are lost (Diez et al 2002, Nguyen et al 2004, Laflamme and Hannah 2005). However, to date, all studies have been ex- perimental rather than clinical. The purpose of this study was to examine the factors associated with two key determinants of outcome during weight loss (eg, mean energy al- location required and relative changes in body composition)in a cohort of client-owned cats with naturally occurring obesity. Factors of *Corresponding author. E-mail: ajgerman@liv.ac.uk Journal of Feline Medicine and Surgery (2008) 10, 452e459 doi:10.1016/j.jfms.2008.02.004 1098-612X/08/050452+08 $34.00/0 Ó 2008 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.