Childhood and adolescence are crucial periods for prevention of obesity, as obese children are five times more likely to be obese at adulthood than lean children. To this purpose, sugar consumption should be reduced. The sugar alcohol erythritol is increasingly popular as sugar substitute in the food industry and is also recommended to diabetic patients. The substance is freely available. Recent acute studies show that erythritol has a positive influence on satiation and gastric emptying without affecting insulin and plasma glucose. In this trial, the investigators aim to assess the effect of a chronic intake of erythritol versus sucrose on insulin resistance in healthy adolescents. EryClot-Pilot: Erythritol is also produced by the human body and possibly elevated erythritol levels in the blood are an indication of an increased risk of cardiovascular disease, obesity or diabetes in the future. In a recently published study, a possible effect of erythritol on blood clotting function was described. In this in vitro experiment, increased blood clotting was observed when erythritol was added to clotting cells (platelets) in the test tube. Studies in humans on blood coagulation after administration of erythritol are missing so far. With a pilot study, the investigators study whether erythritol is detectable in the blood after administration of glucose and fructose. Furthermore, the erythritol level in the blood and a possible effect on the blood coagulation function after administration of erythritol will be investigated. These preliminary tests serve to clarify the data situation so that further studies can be based on them. The preliminary results of the EryClot\_Pilot study indicate that there appears to be no measurable effect of erythritol on thrombocyte aggregation. This implicates that there is a discrepancy between our results and the results reported in a recent published study. This is why we need to assess the effects of erythritol administration on more parameters of blood coagulation as well as in more subjects. Due to a study published in June 2024, there appears the need to investigate the effects of xylitol on blood clotting function as well. EryClot in vitro: In addition to the human EryClot study, we will conduct in vitro experiments (aggregometry assay after addition of erythritol or xylitol in human platelet rich plasma).