Weight gain in gonadectomized normal and lipoprotein lipase-deficient male domestic cats results from increased food intake and not decreased energy expenditure.

Gonadectomy predisposes domestic cats to undesired body weight gain and obesity. The disturbance responsible for this disregulation of energy balance has not been clearly identified. Energy intake and expenditure, body composition and plasma concentrations of leptin, insulin, glucose and triacylglycerol were determined during a 36-wk period in adult male (2-5 y) gonadectomized (n = 8) and intact (n = 8) normal cats and gonadectomized (n = 8) and intact (n = 8) lipoprotein lipase (LPL)-deficient cats. Cats were housed individually in temperature- and light-controlled rooms and continuously provided a commercial dry-type diet. In normal and LPL-deficient cats, body weight increased (P < 0.05) after gonadectomy by 27 to 29%, mostly as a result of fat accretion. There was a rapid increase (P < 0.05) in food intake of approximately 12% after gonadectomy of normal and LPL-deficient cats. The metabolic rate (kJ.kg(-1).d(-1)), determined in normal intact (319 +/- 20, n = 5) and gonadectomized (332 +/- 36, n = 5) cats, did not differ after gonadectomy. After gonadectomy, plasma concentrations of glucose and triacylglycerol did not change, whereas plasma insulin and leptin concentrations increased (P < 0.05), but not coincidentally with body weight gain. A stair-step increase in energy intake, and not decreased energy expenditure, appears to drive the weight gain associated with gonadectomy. Body fat mass appears to increase until the energy intake supports no further expansion. Adiposity signaling through insulin or leptin does not appear to mediate the energy intake effect. LPL deficiency did not preclude development of the overweight body condition. Therefore, gonadectomy-induced weight gain in cats is not a result of changed adipose LPL activity, as previously suggested.