Sugar alcohols such as xylitol and erythritol are increasingly popular as sugar substitutes in the food industry and are also recommended to diabetic patients. Both substances are already in use in the food industry and are freely available. Since the 1970s, beneficial effects on oral health could be demonstrated as oral bacteria were influenced positively. A pilot study recently undertaken in the US (Flint N, 2014) has shown that diabetics profit from a daily intake of erythritol, as this natural sweetener enhances the elasticity of the blood vessels. In this trial, investigators aim to examine whether this effect can be found in a non-diabetic but obese cohort, and whether also xylitol improves vascular function.