The results from animal models of human conditions should be treated with caution because of physiological differences. However, animal models in nutrition have been useful in understanding some conditions when taken in context. Obesity occurs in cats in Western nations just as obesity occurs in the human population. The traditional view is that obesity is caused by overeating, resulting in a positive energy balance that allows a build up of energy which is shunted to storage in adipose tissue. Just as with humans, obesity in cats is associated with a number of diseases including diabetes, liver disorders, oral diseases and well as orthopaedic and dermatological conditions. As with most human cases, the primary treatment for obese cats is energy restriction. The aim is to cause a negative energy balance that gradually allows the use of stored energy as fuel, reducing adiposity.
However, clinical evidence suggests that calorie restriction in cats in not a successful strategy to cause weight loss. As with humans, there is often an initial loss of weight that causes adiposity to reduce. However, after a period of adjustment weigh loss ceases and over time the weight is regained. The reason for this in other species is well recorded, and involves changes in the basal metabolic rate. Energy restriction causes a decrease in energy expenditure that not only opposes further weight loss but then allows weight re-gain once calorie restriction is ended. Exercise appears to have a similar effect to calorie restriction in obese animals. Once the energy balance becomes negative, through increased exercise, energy expenditure at rest falls, preventing further weight loss and increasing the likelihood of rapid weight re-gain.
Energy restriction in cats has been investigated1 in order to assess the decrease in energy expenditure that may follow calorie restriction. The energy expenditure of 10 obese adult cats that were given a reduced calorie diet were measure at baseline, during weight loss and following weight regain. At baseline the cats weighed 6.1 kg, had a body condition score (BCS) of 7.6 out of 9 and 38% body fat. After the period of weight loss, the body weight had fallen to 5.0 kg, the BCS was 5.5 and body fat was 31%. After weight regain had occurred in the cats, body weight rose to 6.2, BCS was 7.7 and body fat was 42%. During these 3 periods, total energy expenditure was 1258, 1025 and 1103 kJ/d, respectively. These results suggest that weight loss in cats causes a decrease in energy expenditure, which remains after weight is re-gained. This appears to be similar to humans, monkeys, dogs and rodents.
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