Differential effects of sucrose, fructose and glucose on carbohydrate-induced obesity in rats

Caloric intakes, body weights, plasma glucose levels and glucose tolerance were examined in male Sprague-Dawley rats given a single standard diet or the standard diet and one of four sources of sugar: 1) a 32% glucose solution, 2) a 32 % fructose solution, 3) a 32% sucrose solution or 4) granulated sucrose. After 50 days, blood was collected from fasted animals for analyses of serum glucose, triglycerides and insulin levels. Livers, kidneys, epididymal and retroperitoneal fat depots and intrascapular brown adipose tissue (BAT) were removed and weighed. Animals given sugar solutions and the standard diet consumed significantly more calories, gained more weight and had significantly more retroperitoneal fat than controls given only the standard diet. Although rats given granulated sucrose and the standard diet did not eat more, they did gain significantly more weight per kilocalorie consumed and had more retroperitoneal fat than controls. Rats given the sucrose solution had significantly more BAT than controls or rats given the fructose solution or granulated sucrose. Rats receiving glucose had significantly more BAT than controls. Access to the fructose or sucrose solutions led to a decreased ability to tolerate an oral glucose load. Animals given fructose had significantly greater serum triglyceride levels than controls or rats given the glucose or sucrose solutions.