A high concentration of dietary carbohydrate is suggested to increase the risk of obesity and diabetes mellitus in domestic cats. To evaluate this, food intake, body weight, fat mass and circulating adiposity-related factors were determined in twenty-four sexually mature (9-12 months) cats assigned to four six-cat dietary groups balanced for body weight and sex. The effect of dietary fat in exchange for carbohydrate at 9, 25, 44 and 64 % of metabolisable energy (ME) in a purified diet of constant protein:ME ratio was studied 13 weeks before and 17 weeks after gonadectomy (GX). Body weight did not significantly change among the cats before GX except for an increase of 17 (SEM 5) % in cats given the highest-fat diet. Following GX, all groups gained body weight, and body fat mass was positively correlated (r 0·50; P,0·04) with dietary fat percentage. Post-GX weight gains were much greater for females (þ39 (SEM 5) %) than males (þ 10 (SEM 4) %). Plasma ghrelin concentration negatively correlated (P,0·02) with dietary fat percentage and, before GX, was greater (P, 0·05) in females than males. Plasma insulin concentration increased with weight gain induced by high dietary fat. Plasma glucose, TAG and leptin concentrations were not affected by dietary fat percentage, GX or weight gain. These data provide evidence that in cats, high dietary fat, but not carbohydrate, induces weight gain and a congruent increase in insulin, while GX increases sensitivity to weight gain induced by dietary fat.
Obesity: Dietary fat: Neutering: Ghrelin: CatsAn evaluation of the nutrient requirements of domestic cats has led to the conclusion that cats are metabolically attuned to carnivorous diets 1 . As such, cats serve as useful models for studies of comparative nutrition and metabolism. Recent epidemiological investigations have yielded evidence which attributes an increased risk for obesity in cats to commercially available, high-carbohydrate, dry-expanded diets as opposed to commercially available, canned, high-fat diets 2 . These observations in cats deviate from experimental finding in the rodent literature, where diets high in fat are found to cause weight gain and induce obesity 3,4 . Mechanisms by which high-carbohydrate diets might cause obesity in cats are speculative. A high constitutive rate of glucose production from amino acid catabolism and a low capacity for glucose disposal are suggested to direct unutilised carbohydrate toward fatty acid synthesis and storage 5 . An alternative mechanism is that high dietary carbohydrate exposure extraordinarily prolongs insulin release, resulting in diversion of dietary fat away from oxidation toward storage in adipose. This latter mechanism seems more plausible than the former because feline liver and adipose tissues appear to poorly utilise glucose for fatty acid synthesis 6 . Ingredients, energy density and palatability of high-carbohydrate, commercial dry-expanded diets are substantively different from those in most commercial canned diets. Because of this, factors other than carboh...