The study aimed to compare the effects of a diet rich in carbohydrates or fat on rat kidneys which play important role in the maintenance of body fluid volume., composition and pH by its absorptive functions.  Rats were fed with a high carbohydrate (HCD), high fat (HFD) or normal diet (control) for 28 days. After the applications, blood samples were collected and the kidneys were removed under anesthesia. HCD and HFD increased but differentially serum glucose, cholesterol and phospholipids. Serum inorganic phosphate (Pi) was increased and urine Pi decreased but serum and urine creatinine were not affected by both HCD and HFD. Alkaline phosphatase (ALkPase) activity increased by HCD but decreased by HFD in brush border membrane vesicles (BBMV). The effect was greater in BBMV from superficial cortex (BBMV=SC) than in from juxtamedullary cortex (BBMV-JMC). However, γ-glutamyl transpeptidase (GGTase) activity was similarly lowered in BBMV-SC and BBMV-JMC by HCD and HFD.  Kinetic studies revealed that increase/decrease of ALkPase activity by HCD /HFD was due to increase/decrease of Vmax and Km values. HCD increased enzymes of glycolysis and TCA cycle but decreased the enzymes of gluconeogenesis and HMP-shunt pathways in the renal homogenates.  HFD lowers the enzymes of glucose metabolism but increased enzymes of gluconeogenesis. The BBM uptake of Pi was increased by HCD and HFD alike but the effect by HCD was more pronounced than by HFD.  Both HCD and HFD increased lipid peroxidation (MDA) and decreased activity of superoxide dismutase and catalase in kidney tissues. In conclusion, consumption of both HCD and HFD increased oxidative stress that caused specific alteration in BBM enzymes, transport of Pi and metabolic activity and perturbed oxidant-antioxidant balance albeit differentially as indicated by the changes observed in relevant enzymes and other parameters.