Effect of CR and spice compounds on plasma glucose and insulin concentrations. Plasma was collected and the glucose (A) and insulin (B) levels were determined by using Glucose Colorimetric Assay Kit and Ultra Sensitive Mouse Insulin ELISA Kit, respectively. Values are means ± SEM, n = 8 mice/group. Means without a common letter differ at P < 0.05. HFD: high fat diet, CR: caloric restriction, C: curcumin, P: piperine.